Stereophonics: Inaural Time Differences

744 Words 3 Pages
Imagine storming the beach of Normandy, France on June 6, 1944. Shell fire from behind almost knocking you flat. Shrapnel flying from your left to your right in a second. Bursts of gunfire directly overheard. The ground shaking as you charge forward. Today, a person does not have to leave the comfort of his or her home to be immersed in this reality. Through the process of stereophonic recording and playback, it is possible to put the consumer directly in the action. This most commonly known as surround sound to the public. Stereophonics is widely used today, but is not a new process. Most living things hear in stereo, humans included. From an evolutionary standpoint this makes a person able to hear approaching threats and avert danger. Localization …show more content…
HRTFs, also known as Head Related Transfer Functions. Basically, this tells the brain how far away a sound is coming from. Binaural cues are a bit more in depth. There are two binaural cues, Interaural Intensity Differences(IIDs) and Interaural Time Differences(ITDs). IIDs create what is known as a Lo-pass filter to the closest ear or ipsilateral ear. It creates sort of a shadow over the farthest ear or the contralateral ear. ITD works by letting the brain know which ear the sound gets to first. This is how ipsilateral and contralateral ears are determined. Sound boils down to time, frequency, and …show more content…
This is what the audience hears. In a left and right speaker situation the outputs of each speaker are interpreted by HRTFs and Binaural cues. From what was mentioned earlier about these, this is how the audience identifies where certain sounds are coming from. It can be seen the easiest in movies. Say the sound of a door slamming happens in the left speaker. In a scary movie setting the audience knows to focus on the left for the danger. Certain tricks are utilized by engineers to give off different illusions. Say for instance that in a left and right speaker situation that the right speaker is +10db louder than the left. A process called binaural summation occurs. What happens is a phantom image of the right speaker appears more inward to make the right speaker seem closer. When in reality, all that has happened is the speaker was turned up a bit. Time also is a factor in these cases. This time there is a .5ms delay on the right speaker. Even if the person is perfectly centered between the speakers, it will make the left speaker seem

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