The term sound localization is used to mean the ability of the listener to identify the origin or location of the sound and its direction (Goldstein 9). For instance, if you are standing in the hall and a friend calls from behind, you will automatically know that he/she is behind without even looking. This is because you can detect where the sound is coming from. Sound localization is also important as it helps the hunter to locate the hiding place of the prey or a person can tell the specific location of an animal. Since it is an important aspect of our lives, much research has been done on this area to try and understand the mechanism of sound localization. According to sound localization, the sound is placed in three types of coordinates systems. These include; azimuth, elevation, and distance coordinate. The azimuth is the horizontal coordinate that refers to the sounds that are located to the right or left in comparison to the listener. For the ear to find azimuth sound it uses interaural time differences (ITD) which refer to the disparities between the sounds reaching each ear. In other terms, ITD refers to the amount of time taken for a sound wave to hit one ear compared to the other ear. The work of ITD is to help the ear distinguish whether the sound is originating from the left or right side. The elevation coordinate uses spectral cues to detect the sound when it is coming from above or below the ears. The ear can detect the location of the sound below or above it by measuring the differences in sound frequency caused by bouncing waves around the pinnae. The spectral cues arise when the head and pinnae of the ear affect the sound frequency (Goldstein 40). The difference between the actual sound and the sound that enters the eye after bouncing around the pinnae is referred to as the directional transfer function (DTF). It becomes difficult to locate the sound if the pinnae are smooth. In addition, a recent study has indicated the likelihood of the disparity of auditory perceptions if a person’s pinnae are altered. There has been little research on the distance coordinates which is used to measure the distance between the person receiving the sound and its origin. The distance cues used by the ear include the movement parallax, sound frequency, reflection, and sound level. The distance will affect the sounds since the atmosphere tends to absorb the higher frequencies. In addition, a sound that is closer to the ear will tend to move across our field of view quicker than those that are far away. In the following paragraphs, problems involving the Azimuth and distance coordinates are discussed.
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Sometimes in our lives, sound localization may break down as a result of various causes. If a person has ear damage resulting in deafness it becomes impossible for him to locate sounds. The ability to locate sounds will eventually decrease or collapse if the auditory cortex is injured. This is because sound localization processing takes place in the auditory cortex of the brain. A person is able to locate specific sound origins due to the timings of neurons in the auditory cortex. Mostly this affects the azimuth sound localization cues. Such individual with this kind of problem requires hearing aids to help them in sound perception. However, a person has to use a pair of hearing aids as one would not work properly (Klingon and Bontecou 880). In addition, if only one of the ears is functioning clearly the ITD cues become useless. Sound localization is important in music halls, theatres, or opera houses because these buildings require sound non-reflective surfaces. A recent study has been conducted on how sound localization is affected by sound-reflecting surfaces. According to the study, the subjects were placed in an anechoic chamber consisting of twenty-seven speakers that were seated at different locations around the room. The subjects were instructed to locate the correct speaker that produced the sound. In addition, a surface that reflects the sound was placed either on the wall, the floor, or the ceiling. The subjects located the sound effect when the reflecting was placed on the floor as compared to when the reflecting surface was placed on the ceiling (Guski 825). This on the other hand is crucial information to architecture to design halls accordingly in order to get the desired sound reflectance.
Goldstein, E. Sensation and Perception. Pacific Grove, CA: Wadsworth-Thomsom Learning, 2002.
Guski R. “Auditory Localization: effects of reflecting surfaces.” Perception 19.6 (1990): 819-30.
Klingon, G.H., and Bontecou, D.C. “Localization inauditory space.” Neurology 16 (1966): 879-886