**Glossary of used terms**

research [31, 32] for amateurs as well as for professional sound engineers. Taking into account the obtained values for all kinds of spectral modification at given octave bands it can be clearly seen that longer exposure to loud signals causes greater uncertainty of sound color assessment but the relation is not proportional: the great increase has been noted when time exposure is 90 min and further prolongation of noise exposition up to 2 h does not influence the standard deviation values for lower and higher frequency regions, so it might be said that the concentration is kept at the same level. It should be also noted that the values of standard deviation are higher for 125 Hz for a modified frequency band than for higher frequencies which clearly

The audibility of timbral modifications depends on the frequency of modified region, the amplitude of peak (or notch) as well as the bandwidth. As it is reported in the literature, changes in sound quality, for example, made by introducing resonances or notches depend on musical material used in audition, the listening environment and reverberation used at a recording process [30]. The most important result of present experiment is that the audibility of spectral changes depends on the level of this modification as well as on the time of disturbing loud music exposure. Moreover, with discontinuous, irregular impulsive, or transient sounds characteristic for speech and musical signals, the test material is less resistible in comparison to the steady sounds. Obtained results are in good agreement with the ones reported in the literature as results of profile analysis [29] as well as the "classical" view on the timbre change perception [28]. It should be noted here that so called traditional view on the timbre perception is based on the intensity discriminations in particular frequency bands while the basic assumption of the profile analysis is that discrimination of the spectral changes is based on the evaluation of the overall spectrum shape involving the memory and interstimuli intervals. The results of experiments provided by both methods are similar in a case of such signals as used in our research. According to this, the ability of the distinguished changes in spectrum are 2–3 dB for listeners with normal hearing. It may be assumed that this fact takes place at the beginning of experiment (before exposure to the loud musical material). For the people with relatively small hearing loss (up to 20 dB) the predicted results of the peak or notch of spectrum modification may be shifted up to 5–6 dB which coincides with our results: the attenuation/amplification must be at 6 dB to be perceived with the greatest accuracy after

On the basis of the obtained results, it may be stated that the temporary threshold shift phenomenon is the important factor that determines perceptibility of changes in spectral and amplitude domains of musical signals. This conclusion results from the way of changes in obtained values for different time of loud music exposure. This is a usual phenomenon especially for 1 kHz because this range of frequency is the most sensitive for human hearing [33] and this fact can help the listeners to take a good decision during sound evaluation. Results of spectral changes detection are convergent with results reported in the literature. According to these results, the TTS measured immediately after loud music exposure ranges from 10 to 30 dB, depends on the

means that uncertainty of spectrum change detection is worse for lower frequencies.

**4. Conclusions**

180 Advances in Clinical Audiology

longer (more than 1 h) presentation of loud music.

**A‐weighting** is the correction of the sound pressure level (SPL) as a function of frequency in such a manner that it reflects human feeling of loudness level of different frequencies. The A‐ weighting curve is defined in the International Standard IEC 61672:2003

**Clarity of sound** is the property of reproduced sound that allows the listener to distinguish the basic components of information. It depends on the degree to which the sound is free from any kind of distortion.

**Closed headphones** are the headphones which have the back of the earcups closed. Closed headphones isolate the ear from external ambient noise and minimize the music leakage out of the earpieces.

**Dynamic compression** is a signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds by narrowing an audio signal's dynamic range. The device which realizes dynamic compression is called a compressor.

**Earphones** are electroacoustic transducers which converts an electrical signal into acoustical one and deliver it directly to the ear.

**Energy dose** is the integral of the square of acoustic pressure over time. The units of energy dose are Pa2 s and Pa2 h. It is also known as sound exposure.

**Front of House (FOH)** is the part of a performance venue which is open to the public, for example, an auditorium and foyer. Front of house sound engineer is normally positioned in a small sectioned‐off area front of house, surrounded by the audience or at the edge of the audience area. From this position, he has unobstructed hearing and a clear view of the performance, enabling the operation of the speaker system, show control consoles and other equipment. In this case, Front of House can refer to both the general audience/public area or to the specific small section from where the show is operated.

**Headphones** are a pair of earphones connected with a bail which is put on the head. The bail provides the necessary downforce of earpieces to the ears.

**Hearing level (HL)** is defined in a similar way as the SPL (see below), except the reference level which is equal to normal threshold of hearing for a given frequency. Hearing level is applied in audiometry for determination of hearing loss.

**Inside or inner earphones** are very small earphones which are inserted directly into ear canal.

**Loudspeakers** are electroacoustic transducers, which convert an electrical signal into acoustical one and radiate it into space. The loudspeakers occur most often as loudspeaker sets, which consist of a few single loudspeakers, enclosure, filters, amplifiers etc.

**Open headphones** have the back of the earcups open. The sound in the ear canal does not depend on the downforce of the earphones to the ears. Open headphones do not block out ambient noise and allow audio leakage out of the earpieces.

**Permanent threshold shift (PTS)**is a permanent shift in the auditory threshold. It may occur suddenly or develop gradually over time. A permanent threshold shift results in permanent hearing loss.

**Public address (PA)** is an electronic sound amplification and distribution system, used to delivery sound with sufficiently high SPL to the public in large spaces: railway stations, airports, stadiums, department stores etc.

**Semi‐open headphones** are a compromise between open and closed headphones. They combine all the positive properties of both designs.

**Sound pressure level (SPL)** is defined as twenty logarithms of the ratio the RMS (root mean square) value of an actual acoustic pressure and the reference level equal to 20 μPa. Unit of the SPL is decibel (dB).

**Temporary threshold shift (TTS)**is a temporary shift in the auditory hearing threshold. It may occur suddenly after exposure to a high level of noise, a situation in which most people experience reduced hearing. A temporary threshold shift results in temporary hearing loss.
