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89 Cards in this Set
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What is amplitude?

The extent of vibratory movement of a mass from its position of rest to that point farthest from the position of rest.

What is Anechoic Chamber?

A specially built room with large wedges of sound absorbing material on all walls, floor and ceiling whose purpose is to provide maximum sound absorption and to keep reverberation to an absolute minimum.

What is an aperiodic sound?

A complex sound that varies randomly over time and does not have a fundamental frequency.

What is an artificial ear?

A device for calibrating airconductino earphones. it consists of a 6 cm3 coupler to connect an earphone to an condenser microphone with cathode follower and a meter that reads in dB SPL. When calibrating insert earphones, a 2cm3 coupler must be used.

What is an artificial mastoid?

A device for calibrating boneconduction vibrators consisting of a resilient surface that simulates the vibrating properties of the mastoid process of the skull and an accelerometer. It is connected to a meter that reads in either decibels or units of force.

What is an Audiometer?

A device for determining the thresholds of hearing. Pure tones at various frequencies are generated, and their levels are increased and decreased until thresholds are found. Outputs may include earphones for airconduction testing, a boneconduction vibrator for boneconduction testing, and one or more loudspeakers for soundfield testing.

Beats....?

Periodic variations of the amplitude of a tone when a second tone of slightly different frequency is produced simultaneously.

Bel?

A unit for expressing ratios of sound pressures in base 10 logarithms.

Brownian motion

The constant random colliding movement of molecules in a medium.

Cancellation?

The reduction of the amplitude of a sound wave to zero. This results when two tones of the same frequency and amplitude are introduced 180 degrees out of phase.

Complex Wave

A sound wave made up of a number of different sinusoids, each with a different frequency.

Complex wave?

A wave made up of a number of different sinusoids, each with a different frequency.

Component?

A pure tone constituent of a complex wave

Compression

The portion of a sound wave where the molecules of the medium are compressed together

Cosine Wave?

A soundwave representing simple harmonic motion that begins at 90 degrees.

Cycle

The complete sequence of events of a single sine wave through 360 degrees

Damping

Progressive diminution in the amplitude of a vibrating body. Heavy damped=amplitude decays rapidly. Lightly damped=amplitude decays slowly. Critcally damped=all vibration ceases before completion of 1 cycle.

Decibel

A unit for expressing the ratio between two sound pressures or two sound powers; one tenth of a Bel.

Difference Tone

The perceived pitch of a tone resulting from the simultaneous presentation of two tones of different frequencies. The tone perceived has a frequency equal to the difference in hertz between the other two tones.

Dyne

A unit of force just sufficient to accelerate a mass of 1 gram by 1 cm/sec2

Elasticity

The ability of a mas to return to its natural shape.

Erg

A unit of work. One erg results when 1 dyne force displaces an object by 1 centimeter.

Exponent

A logarithm, or power to which a number may be raised

Force

The impetus required to institute or alter the velocity of a body

Forced Vibration

The vibration of a mass controlled and maintained by an external impetus.

Formant

A peak of energy in the spectrum of a vowel sound

Fourier Analysis

The mathmatical breakdown of any complex wave into its component parts, consisting of simple sinusoids of different frequencies.

Free field

An acoustic environment with no reverberating surfaces.

Free vibration

The vibration of a mass independent of any external force.

Frequency

The number of complete oscillations of a vibrating body per unit of time. In acoustics the unit of measurement is cycles per second or Hertz

Fundamental Frequency

The lowest frequency of vibration in a complex wave.

Harmonic

Any wholenumber multiple of the fundamental frequency of a complex wave. The fundamental frequency equals the first harmonic.

Hearing Level

The number of decibels above an average normal threshold for a given signal. The hearinglevel dial of an audiometer is calibrated in dB HL>

Hertz

Cycles per second

Impedence

Opposition to sound wave transmission. Comprises the frictional resistance, mass and stiffness and is influence by frequency.

Intensity

The amount of sound energy per unit of area.

Intensity Level

An expression of the power of a sound per unit of area. The reference level in decibels is 10 12 watt/m2 or 10 16/watt/cm2

Inverse Square Law

The intensity of a sound decreases as a function of the square of the distance from the source.

Joule

The work obtained when a force of one Newton displaces an object one meter. (One J is equal to 10 million ergs)

Kinetic energy

The energy of a mass that results from its motion

Localization

The ability to determine the specific location of a sound source

Loudness Level

The intensity above the reference level for a 1000 Hz tone that is subjectively equal in loudness. The unit of measurement is the phon.

Masking

The process by which the threshold of a sound is elevated by the simultaneous introduction of another sound.

Mass

The quantity of a body as measured in terms of its relationship to inertia. The weight of a body divided by its acceleration due to gravity.

Mass reactance

The quantity that results from the formula: two times pi times frequency times mass.

Logarithm

Exponent that tells the power to which a number is raised; the number of times that a number (the base) is multiplied by itself.

Longitudinal Wave

A wave in which the particles of the medium move along the same axis as the wave

Loudness

The subjective impression of the power of a sound. The unit of measurement is the sone.

Mel

A unit of pitch measurement. One thousand mels is the pitch of a 1000 Hz tone at 40 db SL, 2000 mels is the subjective pitch exactly double 1000 mels, and so on

Microbar

A pressure equal to onemillionth of standard atmospheric pressure. 1 bar equals 1 dyne/cm2.

Newton

The force required to give a one kilogram mass an acceleration of 1 m/sec2. 1 N equals 100,000 dyne

Octave

The difference between two tones seperated by a frequency ratio of 2:1

Ohm

A unit of impedance

Ocillation

The back and forth movement of a vibrating body

Overtone

Any wholenumber multiple of the fundamental frequency of a complex wave. it differs from the harmonic only in the numbering used. The first overtone is equal to the second harmonic.

Pascal

A unit of pressure equal to 1 N/m2

Period

The duration of one cycle of vibration. (per second) The period is the reciprocal of frequency...the period of a 1000 Hz tone is 1/1000 second

Periodic wave

A complex sound that repeats over time.

Phase

The relationship in time between two or more waves.

Phon

The unit of loudness level. It corresponds to the loudness of a signal at other frequencies equal to the intensity of a 1000 Hz tone.

Pitch

The subjective impression of the highness or lowness of a sound; the psychological correlate of frequency.

Potential energy

Energy resulting from a fixed and relative position, as a coiled spring.

Power

The rate at which work is done. Units of measurement are watts or erg/second

Pressure

Force over an area of surface

Pure tone

A tone of only one frequency (no harmonics)

Quality

The sharpness of resonance of a sound system; the vividness or identifying characteristics of a sound; the subjective counterpart of a spectrum; timber

Rarefaction

That portion of a sound wave where the molecules become less densly packed per unit of space

Ratio

The mathematical result of a quantity divided by another quantity of the same kind, often expressed as a fraction

Reactance

The contribution to total acoustic impedance provided by mass, stiffness, and frequency

Resistance

The opposition to a force

Resonance

The ability of a mass to vibrate at a particular frequency with minimum application of external force

Resonant frequency

The frequency at which a mass vibrates with the least amount of external force; the natural frequency of vibration of a mass

Reverberation

A shortterm echo, or the continuation of a sound in a closed area after the source has stopped vibrating, resulting from reflection and refraction of sound waves

Sensation Level (SL)

The number of decibels above the hearing threshold of a given subject for a given signal.

Sine Wave/Sinusoidal

Waveform of a pure tone showing simple harmonic motion

Sone

The unit of loudness measurement. One sone equals the loudness of a 1000 Hz tone at 40 dB SPL

Soundlevel meter

A device designed for measurement of the intensity of sound waves in air. It consists of a microphone, an amplifier, a frequencyweighting circuit and a meter calibrated in decibels with a reference of 20 micropascals

Sound pressure level (SPL)

An expression of the pressure of a sound. The reference level in decibels is 20 micropascals

Spectrum

The sum of the componenets of a complex wave.

Stiffness

The flexibility or pliancy of a mass. The inverse of compliance.

Stiffness Reactance

The quantity that results when the stiffness of a body is divided by two times pi times frequency.

Threshold

The level at which a stimulus is barely perceptible.

Transverse wave

A wave in which the motion of the moecules of hte medium is perpendicular to the direction fo the wave

Velocity

The speed of a sound wave in a iven direction

Vibration

To and fro movement s of a mass.

Watt

A unit of power

Wave

A series of moving impulses set up by a vibration

Wavelength

The distance between the exact same point on two successive cycles of a tone

Work

Energy expended by displacement of a mass. The unit of measurement is an erg or joule
