**Various Aspects of Auditory Fatigue Caused by Listening to Loud Music by Listening to Loud Music**

**Various Aspects of Auditory Fatigue Caused** 

Andrzej Dobrucki, Maurycy J. Kin and Bartłomiej Kruk Bartłomiej Kruk Additional information is available at the end of the chapter

Andrzej Dobrucki, Maurycy J. Kin and

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64611

#### **Abstract**

This chapter presents results of research on influence of auditory fatigue on some aspects of listening condition measured among various groups of listeners. Three experiments have been carried out. The aim of the first one was to find the influence of the kind of headphones used by young people on their hearing loss. The second experiment was concerning the temporary threshold shift (TTS) caused by the listening of loud musical signals after several time of sound exposure. The main interest of the third experiment was the detection ability of changes in spectrum of musical samples obtained after several time of listening to the loud music. It turned out that except for frequency of 4 kHz there is no relation between the types of preferred headphones and the shift of hearing threshold while for the frequency of 4 kHz, a statistically important influence of the headphone types on the threshold values was observed. The second and third experiments were carried out under conditions which normally exist in a studio or on the stage when the sound material is recorded and/or mixed. It turned out that after several loud music listening sessions the average value of temporary threshold shift reached more than 3 dB for 1 kHz and increased up to 6–7 dB with an exposure time of 120 min. On the basis of results obtained from the third experiment, it was found that the decrease in ability to detect the spectrum changes for longer noise exposure exists particularly for lower changes (of ±1.5 dB) and at all frequency regions under investigation. It may suggest that the hearing system gets tired for the region of higher frequencies faster than for other bands after listening to loud music. The results may also be influenced by the mental fatigue which occurred after several time duration of permanently played loud sounds, together with demanding tasks. Such conditions involving the mental engagement in a noisy environment, which is referred to the natural scenery of the studio work can significantly reduce the time of exhaustion which causes the decrease of accuracy in solving several tasks. It should be also noted that the tendencies observed within young people culture in listening loud music in order to be isolated from the environment is actually causing not the TTS phenomenon but permanent threshold shift (PTS).

**Keywords:** listening fatigue, perception of spectral changes, temporary threshold shift

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

## **1. Introduction**

The act of listening to musical sounds is usually considered as a kind of recreation, or an impulse to take a rest. But the music can also be considered as a noise not only from the musical structure and composers' point of view—in some cases, listening to the music may not be only a kind of recreation—for particular professionals it is their work. Reinforcement and recording engineers as well as sound producers are the examples of a trade in which the listening process and its conditions may reflect in the final quality of the work. The people working in these professions are subjected to hearing problem, in the same manner as the noise‐exposed workers in an industry. Of course, listening to the musical sounds is different from a simply industrial noise from the psychological point of view: musical sounds are usually nice and desired while the noise means that a particular signal is assessed as awful and unpleasant. Also, the time‐frequency structure of musical signals differs from the consistency of noise which makes listening to music a pleasant act. In the modern entertainment industry, there is one fact which may be considered while talking about the reinforcement of sound, it is the sound focusing techniques which enable to focus energy within a selected region using the special transducers, the line arrays in this case [1]. The energy dose of sound is a basic acoustic variable that determines the magnitude of sound, and the other function of sound focusing technique is to increase the clarity of sound by increasing the magnitude of the direct wave and decreasing the reflections from unwanted directions which result finally in higher sound levels. From the measurement point of view, it is not so simple to determine the actual sound level in all areas occupied by the audience. Moreover, it can be found that the sound level measured by the microphone in a sound field may be different than the level in the ear canal, so the maximum impulsive noise levels were high in the ear canal but the implications for the causes of hearing loss are indistinct because of ear amplification of 3–4 dB in the region of 1–3 kHz [2]. It should be also added that the sound sources (as a loudspeaker set, or PA systems) situated very close to the ear might increase the risk of hearing loss.

It may be fairer to say that working with louder music as well as listening to it over a long period of time may systematically lead to a permanent hearing damage or to a listening fatigue, which makes proper attention being impossible. In the past few years, the trend in sound production industry has been to increase loudness of musical recordings, particularly. Many radio stations as well as record companies have applied large amounts of dynamic range compression and other means of recording process in order to be perceived in today's noisy world. The trend called as "loudness wars" has been reflected in the higher subjective impressions in psychological domain, and the slogan "louder sounds are sold better" has come true [3]. Many young people want to single their minds out of different backgrounds by the use of special kinds of headphones and they listen to the sound material louder, beside the fact that the listened material is louder in comparison to the recordings made in the previous century. Also, the contemporary designed and produced equipment allows the listeners to consume the music in accordance with their way of life [4, 5] and with higher concentrated energy of sound in order to make the proper sensations for the audience [1].

The way of stimuli presentation (via headphones or loudspeaker, or naturally listening of the event) seems to be an important thing causing the hearing loss. Young people do not take into account that the popular or rock music causes the same effects like the higher and longtime exposure to the noise when the earphones are used for listening, due to the average sound level and duration of exposure which simply leads to a listening fatigue. Young people say, we listen to the music that sounds nicely for us and it is not like noise, so why may it be dangerous for our hearing? Sometimes, one can find many pieces of classical music from the twentieth century which are very loud while performed. As an example, the fourth Symphony of Dmitri Shostakovich if given in some fragments, the sound level exceeds 100 dB in the audience area of the concert hall. The main differences between classical and pop‐music are in the time duration of continuous exposure to the sound, a character of musical structure and spectral consistence of stimuli. In popular music, the method used for musical production is very often based on the sound compression, and this compression itself may increase the potential risk of hearing damage [6–8] or a listening fatigue which makes proper attention being impossible.

**1. Introduction**

168 Advances in Clinical Audiology

The act of listening to musical sounds is usually considered as a kind of recreation, or an impulse to take a rest. But the music can also be considered as a noise not only from the musical structure and composers' point of view—in some cases, listening to the music may not be only a kind of recreation—for particular professionals it is their work. Reinforcement and recording engineers as well as sound producers are the examples of a trade in which the listening process and its conditions may reflect in the final quality of the work. The people working in these professions are subjected to hearing problem, in the same manner as the noise‐exposed workers in an industry. Of course, listening to the musical sounds is different from a simply industrial noise from the psychological point of view: musical sounds are usually nice and desired while the noise means that a particular signal is assessed as awful and unpleasant. Also, the time‐frequency structure of musical signals differs from the consistency of noise which makes listening to music a pleasant act. In the modern entertainment industry, there is one fact which may be considered while talking about the reinforcement of sound, it is the sound focusing techniques which enable to focus energy within a selected region using the special transducers, the line arrays in this case [1]. The energy dose of sound is a basic acoustic variable that determines the magnitude of sound, and the other function of sound focusing technique is to increase the clarity of sound by increasing the magnitude of the direct wave and decreasing the reflections from unwanted directions which result finally in higher sound levels. From the measurement point of view, it is not so simple to determine the actual sound level in all areas occupied by the audience. Moreover, it can be found that the sound level measured by the microphone in a sound field may be different than the level in the ear canal, so the maximum impulsive noise levels were high in the ear canal but the implications for the causes of hearing loss are indistinct because of ear amplification of 3–4 dB in the region of 1–3 kHz [2]. It should be also added that the sound sources (as a loudspeaker set, or PA

systems) situated very close to the ear might increase the risk of hearing loss.

It may be fairer to say that working with louder music as well as listening to it over a long period of time may systematically lead to a permanent hearing damage or to a listening fatigue, which makes proper attention being impossible. In the past few years, the trend in sound production industry has been to increase loudness of musical recordings, particularly. Many radio stations as well as record companies have applied large amounts of dynamic range compression and other means of recording process in order to be perceived in today's noisy world. The trend called as "loudness wars" has been reflected in the higher subjective impressions in psychological domain, and the slogan "louder sounds are sold better" has come true [3]. Many young people want to single their minds out of different backgrounds by the use of special kinds of headphones and they listen to the sound material louder, beside the fact that the listened material is louder in comparison to the recordings made in the previous century. Also, the contemporary designed and produced equipment allows the listeners to consume the music in accordance with their way of life [4, 5] and with higher concentrated energy of sound in order to make the proper sensations for the audience [1].

The way of stimuli presentation (via headphones or loudspeaker, or naturally listening of the event) seems to be an important thing causing the hearing loss. Young people do not take into The typical effect of listening to loud sounds is the temporary threshold shift (TTS) or permanent threshold shift (PTS) which play a huge role in the proper assessment of sound while working in a recording studio. The negative effects of TTS may occur when someone is under the noise, or another loud acoustical signal, exposure for a particular time interval, and then having a rest only after the whole work, without breaks for recreation process. The higher sound levels usually influence human concentration in a negative way, like the chaotic visual structures [9] which are based on psychology of perception. The results of a permanent hearing threshold shift of the people working in the entertainment industry as well as the influence of the kinds of equipment used have been presented [10, 11]. The recommendations of a daily dose of noise for sound makers as well as for musicians are not stated because of the nature of work apart from the fact that it may cause permanent or temporary hearing damages.

Physiological and psychological processes connected to a reaction to sound consist of sensational and emotional reactions. The sensational reaction is the effect of a physiological process, which occurs during listening. It arises when stimuli overdraw sensitivity levels, while the emotional reaction is more complex and difficult to analysis because it is not a direct result of received signal features but depends on the habits and conditions of the listener [12]. Noise related to some activities, for example teaching in classrooms, is correlated with performer's fatigue, increases tension and discomfort, and an interference of teaching and speech recognition [13]. Several studies have been conducted to investigate the effects of noise exposure patterns, including noises of different spectra, interrupted noise exposure patterns, and short‐duration noise exposures on TTS in order to find and determine the maximum time duration of acting noise at a particular level, and the resting time, after that the ear can recover to the before‐noise‐state [14–16]. From these studies, a temporary decrease in auditory sensitivity in normal ear was found after exposure to continuous noise levels weighted by A‐curve above 80 dB for long periods. The set of audiograms characteristic for particular hearing loss caused by various types of noise are also presented in the literature and those results can give the directions to the protections in order to avoid the permanent hearing damage. Laboratory studies regarding the human response from noise exposure provide a better control over noise exposure variables, because the TTS—which can be studied under controlled conditions in the laboratory—behaves almost consistently. It is a relatively simple matter to determine combinations of levels, duration, and temporal pattern that produce the same TTS as the standard daily noise dose.

It is known from literature [14, 15, 17, 18] that the greatest effect of TTS occurs first for the range of 2–6 kHz, and this upward shift disappears after a time, usually in 24 hours, but may last as long as a week. If exposure to noise occurs repeatedly without sufficient time between exposures to allow recovery of normal hearing, threshold shift may become chronic, and eventually permanent. This is a specific danger when people who work in noisy environments are exposed to further noise afterward while driving, at home or at places of entertainment.

The facts mentioned above may reflect in an increase of hearing thresholds of the young people consuming today's music in the way that "louder means better". Of course, the higher hearing thresholds induce difficulty in collecting, understanding, and interpreting many information from the human environment which influences the sense of safety and causes the changes in the way of thinking and living together in society. It also may be interesting if the European Standard EN ISO 7029 still remains true in the light of youngsters' way of life and this aspect is the aim of presented research. According to this standard, the hearing thresholds increase with the age of a subject, starting from 0 dB, as recommended for 20‐year‐old people. The authors' research [10] showed that for young people who use to listen to the loud music via headphones the hearing thresholds have been shifted up to 6 dB. Although such hearing is still qualified as "normal" [19] (see also Section 3.1), according to the EN ISO 7029 this value of hearing threshold shift is typical for 40–50 years‐old people. The population of young people with shifted threshold of hearing is growing up year‐by‐year.
