The inner ear hydrodynamics have been studied in a series of experiments on cats. A detailed analysis has been made of the perilymphatic pressure response to square wave pressure pulses applied to the ear canal and middle ear. It was found that the initial pressure response was followed by a rebound pressure response of the opposite phase. It was also found that in most cases each phase of the pressure response could be expressed in terms of two time constants. When the cochlear aqueduct was patent, the perilymphatic pressure response showed almost equal positive and negative pressure changes. However, when the cochlear aqueduct was surgically blocked, the perilymphatic pressure response consisted almost exclusively of the first phase of the response, while the rebound phase disappeared almost completely. The possibility of influencing the inner ear fluid balance in Meniere's disease by external pressure changes is discussed in the light of the present experimental results.

Animals↗

PubMedDate not supplied

Transmission of complex pressure waves through the perilymphatic fluid in cats.

The response of the perilymphatic fluid to complex pressure waves, composed of low-frequency sine waves superimposed on square-wave pressure pulses of varying amplitude was studied. In cats with a patent cochlear aqueduct a pronounced positive pressure change could be induced in the perilymphatic fluid when complex pressure waves were used. The time constants associated with the stabilization of the perilymphatic pressure after the application of pressure complexes were longer than those associated with square-wave pulses alone. The results indicate that the functional patency of the cochlear aqueduct could be influenced by the transmission of complex pressure waves. The results also indicate that when trying to influence the inner ear hydrodynamic balance in patients with Meniere's disease, the effect of complex pressure waves is far superior to the effect of square-wave pressure pulses in patients with an open cochlear aqueduct.

Animals↗

PubMedDate not supplied

Comparison between hearing threshold measurements made with and without the aid of an ear speculum.

The hearing threshold levels of a small group of shipyard workers having differing degrees of hearing impairment were measured five times using the following audiometric techniques: fixed-tone Békésy audiometry with MX 41/AR cushions, fixed-tone Békésy audiometry with an ear speculum, and sweep-frequency Békésy audiometry with an ear speculum. From these data the mean standard deviations of the hearing threshold levels for the frequencies 0.5, 1, 2, 3, 4, 5, 6, 7 and 8 kHz were calculated, thus giving a measure of the accuracy of each method. The hearing threshold levels obtained by the three methods are compared, and the merits of data handling, expressing hearing threshold levels in pascals rather than decibels, are also discussed.

Audiometry↗