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Perception of Changes in Spectrum and Envelope of Musical Signals vs Auditory Fatigue

Kin M. J., Dobrucki A.

Archives of Acoustics

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2016

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Vol. 41, No. 2

323--330

EN

The paper presents results of research on an influence of listening fatigue on the detection of changes in spectrum and envelope of musical samples. The experiment was carried out under conditions which normally exist in a studio or on the stage when sound material is recorded and/or mixed. The equivalent level of presented sound samples is usually 90 dB and this is an average value of sound level existing in control room at various recording activities. Such musical material may be treated as a noise so Temporary Threshold Shift phenomenon may occur after several sessions and this may lead to a listening fatigue effect. Fourteen subjects participated in the first part of the experiment and all of them have the normal hearing thresholds. The stimuli contained the musical material with introduced changes in sound spectrum up to ±6 dB in low (100 Hz), middle (1 kHz) and high frequency (10 kHz) octave bands. In the second part of research five subjects listened to musical samples with introduced envelope changes up to ±6 dB in interval of 1 s. The time of loud music exposure was 60, 90 and 120 minutes and this material was completely different from the tested samples. It turned out that listening to the music with an Leq = 90 dB for 1 hour influences the hearing thresholds for middle frequency region (about 1–2 kHz) and this has been reflected in a perception of spectral changes. The perceived peaks/notches of 3 dB have the detection ability at 70% and the changes of low and high ranges of spectrum were perceived at the similar level. After the longer exposure, the thresholds shifted up to 4.5 dB for the all investigated stimuli. It has been also found that hearing fatigue after 1 hour of a listening influences the perception of envelope which gets worse of 2 dB in comparison to the fresh-ear listening. When time of listening to the loud music increases, the changes in envelopes which can be detected rise to the value of 6 dB after 90-minutes exposure and it does not increase with further prolongation of listening time.

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The noise-induced harmful effect assessment based on the properties of the human hearing system

Kotus J., Kostek B.

Archives of Acoustics

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2008

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Vol. 33, No. 4

435-440

EN

In this paper a new method of assessing noise-induced harmful effects on the human hearing system is described. The method proposed determines the cumulative impact on hearing system produced by the excessive noise taking into consideration properties of the human hearing system. Based on the predicted effects of the noise exposure, the new types of noise indicators are engineered. The evaluation of these indicators employed various types of noise. The indicators proposed can improve assessment of the harmful effect caused by the noise exposure. An influence of the type of the critical band representation of the hearing system (Bark or ERB scales) on the noise indicator effectivness is also discussed.

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Determining the noise impact on hearing using psychoacoustical noise dosimeter

Czyżewski A., Kotus J., Kostek B.

Archives of Acoustics

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2007

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Vol. 32, No. 2

215-229

EN

This research study presents the designed noise dosimeter based on psychoacoustical properties of the human hearing system and, at the same time, evaluation of time and frequency characteristics of noise. The designed noise dosimeter enables assessing temporary threshold shift (TTS) in critical bands in real time. In this way it is possible monitoring the hearing threshold shift continuously for people who stay in the harmful noise conditions. Moreover, the psychoacoustical noise dosimeter (PND) provides the functionality which determines time causing an increase of the assumed hearing threshold shift along with time required for recovery of a hearing threshold toward its initial value. Noise exposure levels, its duration along with hearing examination have been first measured in the acoustically controlled environment. Pure-tone audiometry has been used for hearing examination. This has been conducted in constant time intervals, during noise exposure as well as during resting time (time required for hearing recovery). The examination aims at measuring hearing threshold at 4 kHz. The important part of this study is validation of the dosimeter performance in the real noise exposure situation. In this case the whole noise measurement scenario encompasses both noise exposure effects, and hearing examination before and after noise exposure. The hearing examination has been extended by the distortion products otoacoustic emission method (DPOAE). The measurement results obtained in real conditions have been compared with those which were computed by means of the presented psychoacoustical noise dosimeter.