Kenji Kurakata

Unwanted sounds generated with test tone presentation can spoil extended high-frequency audiometry

Unwanted sounds from a commercially available audiometer were evaluated in terms of their effects on extended high-frequency (EHF) audiometry. Although the manufacturer reported that the audiometer conformed to relevant International Electrotechnical Commission (IEC) standards, the audiograms obtained using the audiometer were erroneous because the subjects had responded falsely to noise generated with the test tone presentation before detecting the test tone. Analyses of acoustic and electric output signals revealed that the audiometer generated most of the unwanted sounds, not the earphones that were used. Based on the measurement results, clinical implications of the measurement results are discussed for conducting more reliable EHF audiometry.

Measurements of the impact sound of golf clubs and risk of hearing impairment

The ball‐impact sounds of golf clubs with metal heads and of a club with a wood head were measured to investigate their different acoustic properties. Hitting was executed using either a swing machine or a human player. Results of these analyses showed that the metal‐head clubs generated sounds around 100 dB (LpA,Fmax). This level was 5–15 dB higher than that of the wood‐head club. The sounds of the metal‐head clubs had greater power in the high‐frequency region of 4 kHz and above compared to the wood‐head club, which particularly increased the overall sound levels. These results suggest that it would be desirable to develop a metal head with pleasant sound qualities, keeping the sound level lower to minimize hearing damage. Some of these measurement data were published in Japanese in a previous paper [K. Kurakata, J. INCE/J 26, 60–63 (2002)].

Do we have better hearing sensitivity than people in the past

Our hearing sensitivity to tones of various frequencies declines progressively as we become older. ISO 7029 describes a method for calculating expected hearing threshold values as a function of age. However, more than 30 years have passed since the ISO standard source data were published. An earlier paper of the present authors [K. Kurakata and T. Mizunami, Acoust. Sci. Technol. 26, 381–383 (2005)] compared hearing threshold data of Japanese people in recent years to the ISO standard values. The results of that comparison showed that the age‐related sensitivity decrease of Japanese people was smaller, on average, than those described in the standard. A large discrepancy was apparent at 4000 and 8000 Hz: more than 10 dB for older males. In response to that inference, the ISO/TC43/WG1 ‘‘threshold of hearing’’ initiated a project in 2005 to explore the possibility of updating ISO 7029. This paper presents a summary of those comparison results of audiometric data and the work in WG1 for revising the standard.

Loudness functions of older people for pure tones and broadband noises

Loudness functions for pure tones and low‐pass filtered noises were obtained by the magnitude estimation to develop a method for evaluating loudness of older people. The subjects were young adults in their twenties with normal hearing and old adults of 60 and over with age‐related hearing loss. The results of the measurements are as follows: (1) There is no significant difference in the slope of loudness functions for pure tones between both age groups, suggesting most of the older subjects do not have large loudness recruitment. (2) The loudness of filtered noises judged by the older subjects decreases as the cutoff frequency of the noises increases. Considering the audiograms of the subjects, the declined ability of hearing at higher frequencies seems to be the cause of the decrease of loudness. (3) The decrease of loudness may be corrected by taking into account the amount of hearing loss of older people because they have no significant loudness recruitment.

Audio signals in domestic appliances evaluated in terms of the hearing ability of older adults

The audio signals used in domestic appliances currently available on the market in Japan were recorded to identify suitable signals for the hearing ability of older adults. The results of the analysis indicated the following three problems: (1) Some appliances use high‐frequency tones around 4000 Hz. Since these sounds are hard for older adults with presbycusis to hear, it would be better to use signals with lower frequencies. However, the problem here is that if the frequency is lowered, then the signal might be masked by domestic sounds whose power would be greater relative to the low‐frequency signals. (2) The signals used by some appliances are too soft. The intensity of some signals should be adjusted to compensate for the hearing loss among older adults. (3) The sounds used in these appliances are often very similar in terms of both timbre and temporal ringing patterns. That may cause confusion because it is difficult to identify which appliance is signaling.

Perceived trajectory of gliding tones through interrupting noise and its underlying frequency‐extrapolation mechanism

The continuity effect was investigated using frequency glides preceding and following a noise burst. First, the perceived trajectory of the glides during the noise was obtained by a method of drawing in which subjects were required to express what they had heard by drawing a line. The drawings showed that they did not simply interpolate the two frequency points at the beginning and end of the noise, but extrapolated the preceding glide through the noise. Second, two psychophysical experiments were conducted to examine the possibility of the frequency extrapolation. In the first experiment, subjects compared the duration of one glide with that of another followed by a noise. In the second experiment, they judged the final pitch of glide just before the noise. The results of both experiments showed that they traced the frequency change of the glide and perceived its extrapolated trajectory. The maximum duration of the extrapolation reached about 120 ms. This mechanism may underlie the continuity effect in g...