Alexander Cohen

Further Investigation of the Effects of Intensity upon the Pitch of Pure Tones

Typical methods for observing pitch changes with intensity for pure tones consist of varying the frequency of one tone of fixed intensity (the comparison tone) so as to match the pitch of a second tone of fixed frequency (the tone under test) when the latter is set at different intensities. Differences between the comparison and test‐tone frequencies, when equated in pitch under these conditions, are ascribed to their intensity differences and used as a measure of the pitch intensity shifts for the test tone. The comparison and test tones may differ in frequency, however, even when they are matched in pitch under equal intensity conditions. These frequency differences, called pitch‐matching errors, may be identical to those noted above for comparable conditions and consequently nullify the apparent pitch‐intensity shifts. This possibility was studied in two experiments which sought to reproduce the pitch intensity relationship as defined by the data of Stevens and Snow. In more than half the comparisons m...

Temporary threshold shifts in hearing from exposure to combined impact-steady-state noise conditions.

Temporary threshold shifts (ITS) in pure tone hearing acuity are reported for 15 subjects exposed in separate 15‐min periods to taped impact sounds [played back at 124‐ to 127 dB peak sound‐pressure level (SPL)], to three levels of filtered (75‐ tn 1200 cps) steady‐state noise (90, 100, 110 dB SPL), and to combinations of the recorded impact sounds with each level of the steady‐state noise. TTSs from all such exposures were typically small, with the largest shifts occurring in the 1000‐ to 3000 cps frequency range. When combined with 90‐ and 100 dB steady‐state noise, the impacts caused less threshold shift than when presented alone. Such TTS reductions were believed due to the relatively greater ability of the steady‐state noise to arouse and sustain the acoustic reflex with its consequent sound‐attenuation effect. The addition of the 110 dB steady‐state noise did not induce a similar result quite possibly because this exposure, by itself, caused threshold shifts equal to or exceeding those of the impac...

Temporary Threshold Shift in Hearing from Exposure to Different Noise Spectra at Equal dBA Level

The intent of this study was to determine whether sound‐level measurements in dBA could adequately depict harmfulness to hearing from exposures to noises differing widely in spectra. Each of 11 male listeners, aged 20–26 yr, were exposed on two separate occasions to three noises whose spectral slopes were −6, 0, and +6 dB per octave band. All such noises were presented for 30 min via an earphone at 100 dBA. Analyses of variance of the post‐exposure threshold data (corrected to 2 mm, TTS2) found insignificant differences due to the spectral variations for both test and retest conditions as averaged across audiometric frequencies 250–8000 Hz. Interactive effects between spectra and test frequencies were significant, the −6 and 0 dB spectral conditions causing relatively more TTS2 at frequencies below 3000 Hz, and the +6 dB spectrum more TTS2 at frequencies above 3000 Hz. Implication of results for noise‐hazard rating schemes using dBA measures are noted.

Temporary Hearing Losses following Exposure to Pronounced Single‐Frequency Components in Broad‐Band Noise

Temporary hearing losses were observed for 20‐min exposures to pure‐tone frequencies (500, 1000, 2000, 4000 cps), which were independently mixed in various strengths with a broad‐band noise to create different exposure conditions involving a strong tonal component in a noise field. The over‐all (combined pure‐tone/noise) SPL for all conditions was fixed at 105 dB and the resultant losses were compared to those caused by equivalent exposures to just the broad band noise (referred to as the continuous‐spectrum‐noise condition). The pure‐tone/noise combinations produced greater threshold losses than the continuous‐spectrum noise primarily when the pure tone was of low frequency (below 2000 cps) and contained most of the available energy in the sound field. These more prominent pure‐tone exposures exceeded the criteria set forth by the U. S. Air Force 160‐3 Noise Regulation for identifying those conditions of strong pure‐tone energy in noise that are believed more hazardous to hearing. However, other pronounc...

Some general reactions to Kryter's paper “Impairment to hearing from exposure to noise”

Reactions offered here (a) urge rethinking on the adequacy of a widely used criterion for defining hearing handicap in view of data referenced in the subject report, (b) criticize the authors evaluations basic to estimating hearing loss risk from known levels of noise exposure and recommending safe limits for hearing, and (c) question the use of proposed complex schemes for rating noise hazards to hearing as derived from presumed relationships between temporary and permanent noise‐induced threshold shifts in hearing.

Threshold Shift in Hearing as a Function of Bandwidth and Mode of Noise Exposure

Fifteen subjects were each given separate 15‐min exposures to three bandwidths of fatiguing sound (whole octave band and 13‐oct band centered at 1000 Hz, pure tone of 1000 Hz) presented in three modes (constant level, variable level, and intermittent). The 13‐oct band SPL were 5 dB below the whole octave‐band levels for the various exposure conditions that, according to the CHABA criteria, should have yielded equivalent threshold shifts (TTS). The pure‐tone SPLs equaled the 13‐oct band levels for one set of exposures, and were 3 dB lower in another set. These latter conditions were intended to verify the increased noxiousness of pure‐tone versus narrow‐band noise stimulation, also specified in the CHABA criteria. Comparisons of the TTS produced by the different bandwidths and modes of noise presentation suggested that the CHABA criteria may error on the conservative side, especially in rating the hazards to hearing of 13‐oct band and variable types of noise exposure. Implications of these findings as reg...

Temporary Hearing Losses for Bare and Protected Ears as a Function of Exposure Time to Continuous and Firing Noise

Temporary hearing losses for frequencies 250–8000 cps were noted for bare and protected ears (tankers helmet) following 6‐, 12‐, and 18‐min exposures to recorded 30‐cal machine‐gun fire and continuous wideband noise of comparable total energy. Threshold losses for both types of noise were generally confined to tones above 1000 cps and tended to become greater with increasing exposure time. Continuous noise caused greater losses than the firing noise under bare ear conditions for the three exposure times. A comparison of these losses against those noted when using the tankers helmet indicated that the helmet gave significant protection against continuous noise but little protection against the firing noise. A second experiment studied the recovery of 4000 cps threshold losses for a 20‐min period following exposure to the noise conditions cited above. Especially for the longer exposure times, rates of threshold recovery from bare ear exposures to continuous noise were slower than those for the firing nois...

Auditory Discrimination and Sleep Deprivation

Eight subjects were given an auditory discrimination test at four separate times each day (3 a.m., 8 a.m., 4 p.m., 11 p.m.) for a four‐day period in which they were deprived of sleep. The test was a tape recording of 72 groups of sounds. Each group consisted of three successive tonal bursts which were presented binaurally. The third tone in each group was identical to either the first or second tone, the unmatched tone differing in varying amounts of frequency, intensity, or duration from the identical tones. The subject had to indicate which of the first two tones matched the third. Four values of frequency (1000 cps, 1010 cps, 1020 cps, 1030 cps), intensity (70 db, 73 db, 76 db, 79 db), and duration (1.0 sec, 1.3 sec, 1.6 sec, 1.9 sec) were used in constructing the tonal groups. Compared to test data obtained under nondeprivation conditions, losses in discrimination were most prominent at 8 a.m. and 4 p.m. on each deprivation day. In contrast, the 11 p.m. tests showed relatively smaller impairments acro...