The current study suggests two models of binaural hearing, which aim to make predictions for inside- and outside-head localisation of a single sound source in the horizontal plane. Both models … Expand. Highly Influenced. View 4 excerpts, cites background. Headphone Localization of Speech. View 2 excerpts, cites results and background. View 2 excerpts, cites background. Auditory localization cues for a double-size head were simulated using an auditory virtual environment where the acoustic cues were presented to subjects through headphones.
The goals of the study … Expand. Neural correlates of sound externalization. View 3 excerpts, cites background and methods. The precedence effect: fusion and lateralization measures for headphone stimuli lateralized by interaural time and level differences.
View 1 excerpt. Localization of Sound from Single and Paired Sources. In-head localization of acoustic images. In general, the larger the object head is relative to the sound wave, the more capable it is of blocking the sound wave.
How big is the sound wave? That depends on its wavelength. For a given size of head, the higher the frequency of the sound wave, the larger the acoustical shadow will tend to be. To understand, think about different sizes of rocks in a fast moving river. The river represents the sound wave and the various sizes of rocks represent different sizes of head. A small pebble or a small head has very little effect on the current or the sound wave.
A large bolder or a large head has a large effect on the current or the sound wave creating an area of relative calm the acoustic shadow just downstream of the bolder. Given the size of most people's heads and the wavelength of the sounds that we can hear, the ILD starts to become an effective localization cue around Hz.
Below Hz, the head is too small to create an acoustic shadow for the frequencies that humans are sensitive to. The ILD can be as large as 30 dB -- about the maximum protection offered by many over the ear hearing protectors.
That is, the difference in the intensity at the left and right ears due to the acoustic shadow can be fairly large. It should be clear that the ILD occurs, but what does it have to do with localization? The ILD systematically varies based on the location of the sound relative to the ears.
A sound that originates directly in front of a person will be equally distant to the two ears assuming the person is looking directly at the sound source and any acoustic shadow that arises will be the same for the two ears because heads are roughly symmetrical. Thus, sounds coming from directly in front of a person will have an ILD of 0. A sound that is coming from a few cms from the left ear will be five or more times closer to the left ear than to the right ear.
Also, if it is a higher frequency, the whole side of the head is there to block it, creating a relatively large acoustic shadow. If you move a sound source in a circle around a person's head, the ILD will be largest when the sound source is directly to the side of either ear and smallest when directly in front of, or behind the head.
The ILD decreases somewhat uniformly as the sound source moves away from the ear toward the front and then increases somewhat uniformly as it moves away from the front toward the other ear.
Being good students of perception, you will undoubtedly want to know the physiological basis of the ILD. The interaural time difference or ITD is the difference in when a sound reaches one ear compared to reaching the other ear. The ITD also arises because the ears are usually not the same distance to the sound source.
Because the sound wave often has to propagate a little farther to reach one ear compared to the other, and sound waves take time to propagate, one ear will often hear the sound a little before the other ear does. Because the ears are relatively close together and sound moves relatively quickly, this difference is often very small.
Question: Where can a sound originate so that its ITD is 0? In conjunction with the previous question, what does this tell us about sounds originating from these locations? It is fairly simple to calculate the ITD for a sound in any given location relative to a head. The following figure shows the ITD for sounds located at various angles relative to looking straight ahead. The Y axis shows the difference in the arrival times to the left ear relative to the right ear. Positive values indicate that the sounds arrives at the left ear first while negative values indicate that the sound arrives at the right ear first.
The figure clearly indicates that there is a systematic relation between the location of a sound source at the difference in the times that the sound arrives at each ear. Percept Psychophys — Google Scholar. Mills AW On the minimum audible angle.
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