Cartilage conduction hearing.

Sound information is known to travel to the cochlea via either air or bone conduction. However, a vibration signal, delivered to the aural cartilage via a transducer, can also produce a clearly audible sound. This type of conduction has been termed "cartilage conduction." The aural cartilage forms the outer ear and is distributed around the exterior half of the external auditory canal. In cartilage conduction, the cartilage and transducer play the roles of a diaphragm and voice coil of a loudspeaker, respectively. There is a large gap between the impedances of cartilage and skull bone, such that cartilage vibrations are not easily transmitted through bone. Thus, these methods of conduction are distinct. In this study, force was used to apply a transducer to aural cartilage, and it was found that the sound in the auditory canal was amplified, especially for frequencies below 2 kHz. This effect was most pronounced at an application force of 1 N, which is low enough to ensure comfort in the design of hearing aids. The possibility of using force adjustments to vary amplification may also have applications for cell phone design.

Temporal integration of the contralateral acoustic reflex threshold for a 1000 hz tonal activator and its age-related changes.

BACKGROUND: Previous research has noted an age effect on the temporal integration of the acoustic reflex for a noise activator. PURPOSE: To determine whether the age effect earlier noted for a noise activator will be noted for a tonal activator. RESEARCH DESIGN: Comparison of ARTs of younger and older groups at activating stimulus durations of 12, 25, 50, 100, 200, 300, 500, and 1000 msec. STUDY SAMPLE: Two groups of adults with normal-hearing sensitivity: one group of 20 young adults (ten males and ten females, ages 18-29 years, with a mean age of 24 years) and one group of 20 older adults (ten males and ten females, ages 59-75 years, with a mean age of 67.5 years). RESULTS: A significant main effect for duration was obtained. That is, as the duration increased, the acoustic reflex threshold for the 1000 Hz tonal activator decreased. The interactions of duration x age group and duration x hearing level were not significant. There was a nonsignificant main effect (p = .889) for the between-subjects factor of age. CONCLUSION: Results contradict the findings for broadband noise.

A historical perspective on digital hearing AIDS: how digital technology has changed modern hearing AIDS.

This article provides the author's perspective on the development of digital hearing aids and how digital signal processing approaches have led to changes in hearing aid design. Major landmarks in the evolution of digital technology are identified, and their impact on the development of digital hearing aids is discussed. Differences between analog and digital approaches to signal processing in hearing aids are identified.