Differences in noise doses achieved by simultaneous registrations from stationary and ear-borne microphones.
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Audiology↗
Biomedical subjects
H Håkanson
Publications and source records attributed to H Håkanson.
Comparison of the hearing threshold measured by pure-tone audiometry and by Békésy sweep audiometry.
The hearing thresholds of 115 subjects, workers in a shipyard, were determined both by Békésy sweep audiometry and by conventional individual pure-tone audiometry at fixed audiometric frequencies. The Békésy method gave the lowest values for the hearing thresholds. It has been possible to find a useful linear relation between pure-tone and Békésy hearing thresholds. With the help of a retest experiment it has been established that the standard deviations of hearing thresholds, obtained under similar conditions in a pure-tone investigation, are about twice as large as those obtained in a Békésy investigation.
Adult↗
Comparison of the hearing threshold measured by manual pure-tone and by self-recording (Békésy) audiometry.
The hearing threshold of 115 subjects aged 25--63 years and working on a shipyard were determined both by Békésy sweep audiometry and by conventional manual octave pure-tone audiometry at fixed audiometric frequencies. The attenuation rate was 2.5 dB s-1 with pulsed-tone presentation and the sweep time from 0.25 to 10 kHz was 400 s for the Békésy audiometer. Manual pure-tone audiometry was performed in 5-dB steps. The Békésy method gave the lowest values for the hearing thresholds. It has been possible to find a useful linear relation between pure-tone and Békésy hearing thresholds. With the help of a retest experiment, it has been established, that the standard deviations of hearing thresholds obtained under similar conditions in a pure-tone investigation are about twice as large as those obtained in a Békésy investigation.
Adult↗
The effect of static middle ear pressures on the hearing threshold.
The effect of static tympanic pressure gradients on hearing sensitivity was studied by introducing relative underpressure of 5, 10 and 15 cmH2O in the middle ear cavity of six normal ears. A self-recording Békésy audiometer was used to measure the hearing threshold shifts during middle ear pressure equilibrations. The threshold loss was most prominent for 0.5 and 1 kHZ and less for 4 kHZ. A threshold gain was shown for 2 and 6 kHZ. Over all test frequencies the threshold shifts were increased with higher relative underpressure in the middle ear cavity. In order to evaluate the hearing impairment caused by noise, it is therefore important to control the middle ear pressure before hearing is tested. A small change in middle ear pressure can be ignored when using the summed hearing thresholds between 2 and 8 kHZ.
Audiometry, Pure-Tone↗
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↗
Hair cell damage in the inner ear of the guinea pig due to noise in a workshop.
Guinea pigs were exposed to noise in various workshops at a shipyard. The equivalent sound level ranged from 87 to 90 dB(A) and the exposure time was 30 days of 8 hours. The numbers of lost outer hair cells were greater than in control animals, thus establishing a relation between the number of lost hair cells and the total noise dose. A comparison between the results obtained here and results obtained in laboratory experiments shows that although many physical sound parameters may be identical, the effect on the hair cells can be quite different. In particular, the total noise dose is not a parameter which can be directly related to hair cell loss. The most probable explanation for the difference in damage between the laboratory and workshop animals seems to be the rest periods of 16 hours between each of the 8-hour exposure periods.
Animals↗