Above 1500 Hz, where the effect of the time delays is less significant, the intensity difference of the sounds between ears, or ILD, has been listed as a cue for localization. This ITD is recognized as a cue in localization of sounds below 1500 Hz. For sounds below 1500 Hz, where the wavelengths of the sounds are greater than the dimension of the head, the head causes a significant time delay for sounds to travel from one side of the head to the other. This head-shadow effect results in a change of intensity level (interaural level difference, or ILD) and time of arrival (interaural time difference, or ITD) of the same sounds at the opposite ear. Left/right: The head casts a shadow on sounds that originate from one side of the head.Localization on the horizontal plane involves comparison of the same sound received at the two ears (ie, binaural comparison for left/right) or between two surfaces of the same ear (ie, front/back). A listener studies these characteristics (which are described as cues) originating from all directions on the horizontal and the vertical planes to identify the origin of the sound. How Do We Localize?Ī sound source has different temporal, spectral, and intensity characteristics depending on its location in the 3-D space. Fortunately, the application of digital signal processing and wireless transmission techniques in hearing aids has helped preserved the cues for localization.
Hearing loss results in a reduction of localization ability 1 however, the use of amplification may not always restore localization to a normal level. Being able to localize also allows the listener to turn toward the sound source and use the additional visual cues to enhance communication in adverse listening conditions. It is also important for safety reasons such as to avoid oncoming traffic, an approaching cyclist on a running path, or a falling object. The ability to localize sounds provides a more natural and comfortable listening experience. Localization is the ability to tell the direction of a sound source in a 3-D space. Tech Topic | Hearing Review September 2014īy Francis Kuk, PhD, and Petri Korhonen, MSĪn introduction to localization, factors that influence localization when wearing hearing aids, and what steps can be taken to improve localization ability for hearing aid users.
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