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213 Cards in this Set
- Front
- Back
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of these 4 which does not happen often: transmission, diffraction, absorption, reflection
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diffraction
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define transmission
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the amount of the original energy that is present after sound has passed from one propagation medium through some interface to a 2nd medium
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the opposition by some system (electrical, mechanical, acoustical) to the flow of energy is...
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impedance
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what does impedance consist of? (3 parts)
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mass, compliance, resistance
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what are the reactive components of impedance?
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mass and compliance
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resistance does what to frequencies?
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the same thing to all frequencies
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true or false: mass acts agaist low frequencies
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false
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mass or stiffness acts against low frequencies?
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stiffness
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define reflection
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sound that is not absorbed or transmitted but rather bounces off the interface surface
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what can reflection lead to?
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standing waves
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what are standing waves?
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positions in an enclosure where the sound seems louder or softer
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what 3 things are directly related to impedance characteristics?
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transmission, absorbtion, reflection
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the acoustic equivalent of friction is?
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absorbtion (sound energy being converted to heat)
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what is the highest absorbtion coefficient?
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1.0
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which has a high absorbtion coefficient: brick wall or glass?
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glass .05 (brick wall .03)
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define diffraction
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when the wave front is required to bend around an object (object was invisible to sound wave)
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whether diffraction occurs depends upon the relationship between...
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size of object and wavelength
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true or false: most sounds are complex, so not all of the frequencies in the sound may diffract
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true
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which type of frequencies are most likely present when diffraction is occuring?
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low
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how do you tell where the sound is coming from when diffraction has occurred?
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time of arrival
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a sound field is ____ _____ ____
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any enclosed structure
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in a free field, sound travels _______
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unobstructed
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what is reverberation?
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an echo, time off arrival differences between the incident waves and reflective waves
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what are anechoic chambers?
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approximate free field situation
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in what field does the inverse square law apply?
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far field
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what are the three sound fields?
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near, far, diffuse
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how many dBs do you lose every time you double the distance in the far field?
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6 dB
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what is the maximum reverberation time allowed in rooms? (when building)
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.5 seconds (too much causes masking and speech confusion, too little causes a dead room = uncomfortable)
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attentuation means?
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softer or less
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what does the inverse square law predict?
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how the energy will be reduced as you move away from the source
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true or false: in reference to the inverse square law, energy amount stays the same, but area increases which reduces intensity
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true
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What is the inverse square law for intensity formula?
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10 log D1/(D2)²
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What is the inverse square law for pressure formula?
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20 log (square root of) D1/(D2)²
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anytime the output is different than the input is _________.
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distortion
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what is a linear output system?
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the output is the same as the input or the ouput is proportional to the input (amplifiers)
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what type of distortion causes peak clipping?
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frequency distortion
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what type of distortion involves sum and difference tones?
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intermodulation distortion
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What occurs in time/phase distotion?
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time/phase relationships between frequencies are no longer maintained
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true or false: distortion should not occur in a healthy ear
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false, it does occur in a healthy ear with healthy hair cells
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mechanical resonance is based on ___________, _________, and __________.
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mass, stiffness, and resistance
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mass and stiffness reult in a "______ ______".
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natural frequency
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resistance results in a decay of amplitude over time called "____".
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damping
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energy imparted to a tuning fork results in free vibrating motion at the _______ ______ or ______ _________.
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natural frequency or resonant frequency
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impedance =
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force (either mass or stiffness)
____________ velocity |
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mass + stiffness =
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reactance
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mass reactance has a positive or negative phase angle? why?
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positive because it attains a maximum value before velocity does
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stiffness reactance has a positive of negative phase angle? why?
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the force attains a maximum value after velocity does.
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mass reduces what type of frequency energy?
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high- frequency
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stiffness transfers what frequencies best?
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high frequencies
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what determines the optimal frequency?
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the combination of mass and stiffness
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a system is called "________ ______" for frequencies below Fc.
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stiffness dominant
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a system is called "________ _______" for frequencies above Fc.
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mass dominant
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what is the resonant characteristic (Fc)?
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the frequency at which a signal resonates
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If force is applied to an object with pure mass, the force will leave the mass with....
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90 degree (ahead)
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If force is applied to an object with pure stiffness, the force will leave with...
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90 degree lag
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resonance curve is also called? (2 names)
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filter curve and transfer function
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on a resonance curve, a lot of mass forces the resonance curve up or down? and for a lot of stiffness?
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down; up
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what determines damping?
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resistance (that is, frequency-independent attenuation)
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middle ears in all mammals are primarily mass or stiffness dominated?
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stiffness (very little mass)
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resonance characteristics depend upon: (4)
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-volume of the cavity
-area of the aperture -coupling factors -surface characteristics of the cavity |
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the relationship between the size (volume) of the cavity and the rate of vibration is....
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indirect - the greater the volume of the cavity the slower the rate of vibration (lower frequencies)
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the relationship between cavity opening size and the rate of vibration is _______.
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direct - the larger the opening the more rapid the vibration (higher frequencies)
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what are the 2 types of coupling factors?
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loosely and tightly coupled
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explain loosely coupled resonators.
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resonators tend to work independently from one another
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explain tightly couple resonators and give an example.
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resonators work together, affect one another.
example: the vocal tract (oral cavity and trachea) |
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Name the human cavity resonators. (5)
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1. trachea-bronchial tree
2. laryngeal cavities 3. pharyngeal cavities 4. oral cavity 5. nose |
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true or fasle: bends in the tract have a great effect on its resonance.
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false; little effect
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regions of energy that have been reinforced by the resonancy of the tube are...
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formats (they are not frequencies any more)
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who has more resonance characteristics: males, babies, or females
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males (then females, then babies)
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a tube that is open at one end has what type of wave resonators?
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1/4 wave resonators
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a tube that is closed on both ends has what type of wave resonators? open both ends?
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1/2 wave resonators (both)
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true or fasle: bends in the tract have a great effect on its resonance.
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false; little effect
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regions of energy that have been reinforced by the resonancy of the tube are...
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formats (they are not frequencies any more)
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who has more resonance characteristics: males, babies, or females
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males (then females, then babies)
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a tube that is open at one end has what type of wave resonators?
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1/4 wave resonators
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a tube that is closed on both ends has what type of wave resonators? open both ends?
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1/2 wave resonators (both)
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at the point where the waves cross in a tube _____ exist, there is zero velocity
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nodes
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at the point of maximum velocity in a tube there are _______.
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nodes
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what is the lowest frequency that will resonate in a one-end open tube?
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one that has a wave length 4 times longer than the tube
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if the wave does not come to zero at the closed end of a tube, what will occur?
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standing waves
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what are examples of quarter-wave resonators in the human body?
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ear canal and vocal tract
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true or false: 3/4, 5/4, ..... waves also fit nicely in a 1/4 wave resonator.
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true
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what is the formula for one open ended tubes?
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Fn = (2n-1) s
----------- 4L |
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true or false: tubes closed at one end and open at the other do not resonate to even harmonics
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true
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what is the speed of sound in centimeters per second?
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34,000 cm/sec
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true or false: tubes closed at both ends include even harmonics.
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true; odd and even harmonics are present.
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wath is the formula for tubes closed at both ends?
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Fn = n(c)
------- 2L |
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What wavelengths fit into a tube that is closed at both ends?
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1/2, full, 1 1/2, .....
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in which sound field does the sound energy attentuate in a predictablemanner as distance is increased?
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far field
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the __________ the cavity, the higher the resonance.
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smaller
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materials that are more absorptive than others have a low or high absorption coefficient.
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high
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true or false: a time-domain of sound shows the dimension of time and amplitude.
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true
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true or false: a square wave may be created by adding infinite number of even-numbered harmonic sine waves.
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false
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true or false: a signal with 100 hz and 300 hz both started at 0 degrees sounds the same to the human ear as a signal where 100 hz starts 90 degrees before 300 hz
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true
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what are harmonics?
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frequencies related to the fundamental by a ratio of whole number (i.e. 1:2, 1:3, 1:4, ...)
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the lowest frequency in a signal is called the __________ ___________.
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fundamental frequency
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If 200 Hz is the 14th harmonic, which overtone is it?
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13th
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what are the properties of a square wave?
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-always include a fundamental frequency
-all odd harmonics (no evens) -all start at the same phase (usually 90 degrees) -6 dB difference between octaves |
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true or false: square waves can be used to keep time for things.
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true
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what are the two different domains?
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time and frequency
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time domains display _______.
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waveforms
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frequency domains display ________.
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spectrums
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what are the two types of frequency domains?
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amplitude and phase
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what are the characteristics of a time domain?
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-instantaneous amplitude across time
-amplitude is Y axis (ordinate) -time is the X axis (abscissa) |
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what are the characteristics of a frequency domain?
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-requires 2 graphs: amplitude and phase
-amplitude is most important. phase is required for completeness (to recreate wave) -time is discared (infinitely repeating signal assumed) |
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every frequency in a signal is a _________.
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harmonic
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fundamental frequency is always the ________ frequency in a signal.
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lowest
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_______ waves are only pure if they've been turned on gradually and left on for awhile.
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sine (puretones)
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what is a transient?
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serve as the identifiers of sound; allows us to make judgments of sound (broad spectrums)
-turned onquickly and/or left on only briefly |
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what are the 6 different types of waves?
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-sine
-square -triangular -sawtooth -white noise - ?? (letter c on p. 5 of section b) |
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what wave form is the driving signal for the vocal tract?
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triangular waves
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sawtooth waves contain what type of harmonics?
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odds and evens
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what are the rules for presenting a pure tone?
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rise time of 25 milliseconds and duration of 200 milliseconds
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__________ _________ are the abrupt onset of longer signals.
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transient signals
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what is the difference between a square wave and a triangular wave?
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12 dB difference (roll-off) between octaves for triangualar waves; 6 dB difference for square waves
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what anatomical structure produces the triangular wave?
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glottis
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vowel sounds are periodic or aperiodic in nature?
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periodic
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consonants are periodic or aperiodic in nature?
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aperiodic (noise is too)
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what is fourier analysis?
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any complex, periodic wave can be broken down into a sum of simple sinusoids with differing frequencies, amplitudes, and phases
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describe a helmholtz resonator.
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-hollow glass or metal bulb with a narrow tube leading out for demonstration acoustic resonance
-the fundamental oscillation is generated by blowing into the opening or tapping on the outside of the bulb. -can put a complex sound thru this and find out which frequencies are present |
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the _______ the tube the more resonances.
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longer
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what are the characteristics of white noise?
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-random waveform
-equal energy at all frequencies -often created by air turbulence -no fundamental frequency -no harmonics -aperiodic |
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vowel sounds are periodic or aperiodic in nature?
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periodic
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what is resonance?
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the place where __?___ vibrates most easily
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consonants are periodic or aperiodic in nature?
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aperiodic (noise is too)
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devices or separating portions of a complex wave form is _____.
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filters
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what is fourier analysis?
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any complex, periodic wave can be broken down into a sum of simple sinusoids with differing frequencies, amplitudes, and phases
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what is transfer function?
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the difference between the input and the ouput to a system
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vowel sounds are periodic or aperiodic in nature?
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periodic
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describe a helmholtz resonator.
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-hollow glass or metal bulb with a narrow tube leading out for demonstration acoustic resonance
-the fundamental oscillation is generated by blowing into the opening or tapping on the outside of the bulb. -can put a complex sound thru this and find out which frequencies are present |
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consonants are periodic or aperiodic in nature?
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aperiodic (noise is too)
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what is periodicity?
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?? (look up)
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the _______ the tube the more resonances.
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longer
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what is fourier analysis?
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any complex, periodic wave can be broken down into a sum of simple sinusoids with differing frequencies, amplitudes, and phases
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what are the characteristics of white noise?
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-random waveform
-equal energy at all frequencies -often created by air turbulence -no fundamental frequency -no harmonics -aperiodic |
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describe a helmholtz resonator.
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-hollow glass or metal bulb with a narrow tube leading out for demonstration acoustic resonance
-the fundamental oscillation is generated by blowing into the opening or tapping on the outside of the bulb. -can put a complex sound thru this and find out which frequencies are present |
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what is resonance?
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the place where __?___ vibrates most easily
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the _______ the tube the more resonances.
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longer
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devices or separating portions of a complex wave form is _____.
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filters
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what are the characteristics of white noise?
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-random waveform
-equal energy at all frequencies -often created by air turbulence -no fundamental frequency -no harmonics -aperiodic |
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what is transfer function?
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the difference between the input and the ouput to a system
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what is resonance?
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the place where __?___ vibrates most easily
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what is periodicity?
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?? (look up)
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devices or separating portions of a complex wave form is _____.
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filters
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what is transfer function?
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the difference between the input and the ouput to a system
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what is periodicity?
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?? (look up)
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name the 4 types of filters
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-high pass
-low pass -band pass -band reject |
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the ________ _______ filter rejects low frequencies and allows high frequencies through.
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high pass
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true or false: low pass filters reject low frequencies and let high frequencies pass.
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false
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which filter passes frequencies on the low and high ends but rejects the middle freqencies? which passes the middle frequencies only?
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band reject; band pass
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what carries 95% of the intelligibility in speech?
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consonants
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what has 95% of the power in speech?
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vowels
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vowels carry ___% of intelligibility for speech.
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5
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true or false: consonants only carry 5% of the power in speech.
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true
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____% of intelligibility occurs around ______ Hz for speech.
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75; 2000
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in a low pass filter, vowels or consonants are rejected
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consonants
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in a high pass filter, vowels or consonants are mainly rejected?
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vowels
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what frequency does the human mouth tend to resonate around? what changes the resonance?
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2000 Hz; the tongue
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what is the notch filter used for?
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to get rid of specific bands of frequency
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true or false: analog is continuous.
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true
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true or false: digital is continuous
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false (non-continuous)
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define compacidance
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opposite flow of low energy frequencies
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________ is the electrical equivalent of mass and opposes high frequency energy.
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inductance
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outlets energy = _____ Hz
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60
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what are the characteristics of analog representation of speech?
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-continuous (every time has a value)
-simple equipment -trouble with noise and distortion -difficult to maintain -inflexible |
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what are the characteristics of digital representation of speech?
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-discrete (only specific times have values)
-complex equipment -noise and distortion as low as desired -easy to maintain -flexible |
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for digital representation of speech, numbers that represent frequencies we don't want are _________.
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disregarded
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explain the representation of speech in a digital recorder
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DIAGRAM!
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what are the digitization parameters?
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-sampling rate
-bits of quantization |
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what determines frequency resolution?
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sampling rate
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what does bits of quantization determine?
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amplitude resolution
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what is the niquist frequency?
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sample at more than twice the highest frequency in the signal
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why do we sample above the niquist frequency?
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upon playback, all distortion is guartanteed to be above the niquist frequency
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how do we prevent aliasing?
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sample at the Niquist frequency
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how many samples you have to take is ________ related to the complexity of the signal.
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directly
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what is aliasing?
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higher frequency signals being wrapped around to the low frequency side of the spectrum
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if not enough sampling is used for a waveform, a different waveform is produced. this results in a lower or higher frequency?
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lower
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for bit quantization, what base is always used?
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2
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how many steps are there in 16-bits?
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65,536
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why do we need to make sure enough bits are used during quantization?
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to make sure the maximum amplitude is represented
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what dB range does speech have?
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40 dB
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what type of filtering should be used to eliminate any distortion above the niquist frequency?
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low pass filtering
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what formula is used to tell how many dBs of range there are in speech?
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20 log 2(exponent w)
--- 1(reference is always 1) |
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what bit are most cd players, recorders, etc.?
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16
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in reference to the far field, the sound diminishes _______ with the distance from the source.
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inversely
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in reference to the far field, the overall intensity decreases at a rate equal to the __________________________.
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square of the distance
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in order to digitize sounds what 2 things do we need to capture the signal present?
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frequency and amplitude resolution
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the cut-off frequency of filters is defined at the ________ _____ _________ or _______ ________ _______ ______.
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half intensity point or 3 dB down point
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by reducing the intensity in half, how much of a difference is this in dBs?
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3 dBs
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what is the slope of a filter referred to as?
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rejection rate
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true or false: a transducer changes acoustic energy into something we can see.
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true
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true or false: the lower the roll-off value the more selecive the filter.
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false - the higher the roll-off value
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what ar typical band measurements?
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1 octave and 1/3 octave
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what type of band measurements are better for ragid waveforms?
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1/3 octave (more points are plotted)
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true or false: the higher the intestity the more frequencies we can hear.
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true
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what weighting scale is most often used for speech signals? why?
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A scale becaus it is most representative of the MAP curve
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what are the 3 weighting scales?
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A, B, and C
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If the A scale had lower dB value than the C scale,........
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there would be more low frequency energy in the spectrum.
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why do humans have less sensitivity in the low frequencies?
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because the auditory system is stiffness dominated. little mass (mass transfers low frequencies better)
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what weighting scale do we use for 24-55 dB SPL?
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A scale (reported as dBa)
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what scale do we use for 55-85 dB SPL?
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B scale
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what weighting scale do we use for over 85 dB SPL?
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C scale
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A _________ changes a "real world" event (e.g. acoustic signal) into an electrical event (e.g. voltage change) that you can store and/or utilize.
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transducer
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Name different types of transducers. (at least 4)
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-microphones
-loudspeakers (headsets, earphones) -strain gauges -accelerometers -thermistors -vibrotactile devices -video cameras -video displays |
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what is a major problem when using transducers?
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need to prevent it from tainting results (don't want mass and stiffness to influence the outcome)
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what are the characteristics of a transducer?
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-real-world signal in --- volts out
-volts in --- real-world signal out -should provide faithful representation of changes in the waveform (the ideal) -natural properties of the transducer (mass, stiffness) should not alter the waveform |
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if there is too much mass or stiffness in a transducer, what will it act as instead?
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filter
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what does a strain gauge measure?
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the force of lips
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how is an accelerometer measured?
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apply the device to something, the natural lag (difference) produces the result (measurement)
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for intermodulation distortion: 500 Hz and 1200 Hz were put into a signal. what second order tones came out with them?
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F1 + F2 = 1700 Hz
F2 - F1 = 700 Hz (distortion comes in at the 2nd order tones) |
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what are 3rd order tones also known as? and what is done to F1 or F2 to get these tones?
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-cubic difference tones
-one of them is multiplied by 2 |
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what is resonance?
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the frequency at which the tube vibrates the greatest
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_________ is the resonance characteristic of our vocal tract.
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formant
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