Abstract
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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