After reading this article you will learn about :- 1. A Typical Pop Group 2. Typical Noise Levels 3. Hearing Damage.
A Typical Pop Group:
Pop music (an abbreviation for “popular music”) had its origins in the jazz and swing bands of the 1940’s and 1950’s. These progressed to the rock and roll era of I960’s and evolved into the present-day pop groups and discotheques.
Although of foreign origin, pop music is rapidly gaining its popularity among Indian audiences, particularly young urban people. Most college students, for example, prefer pop music over the Indian classical or light music.
An important feature of pop music is that it is invariably very loud, since its fans like it that way. Current disco amplifiers produce power outputs ranging from 500 to 1,500 watts.
Thus pop music customers get what they want and pay for-and even the neighbours are forced to share it. It appears that, to the younger audiences of pop music, “louder is better and loudest is best”. In current pop groups, each musical instrument may have an amplifier of up to 200 watts.
A typical pop group may have the following instruments:
(a) Lead guitar playing ‘into two 50-watt amplifiers,
(b) Rhythm guitar with similar amplifiers,
(c) Bass guitar playing into two 100- watt amplifiers.
In addition to this, each drum and cymbal has a microphone in front of it. Each singer will also have a microphone. The signals from these numerous microphones are fed into a mixer which, in turn, feeds two 200-watt amplifiers with loudspeakers at each side of the stage. All this add up to a total of 800 watts of power, plus the mechanical output of the drums.
Typical Noise Levels:
At the beginning of a typical pop concert, the noise level may be in the range of 95 to 100 dB (A) at the mixing position. This is more than sufficient to cause Temporary Threshold Shift in the “mixer” (a person responsible for mixing the signals from various instruments), the pop group and the audience.
The mixer tries to keep the sound level apparently constant at his position and the net result of his Temporary Threshold Shift mentioned above is that he gradually raises the sound level as the evening progresses.
In addition, there is an extra rise in excitement and hence the sound level-in order to obtain the ideal climax to each “set”. These two phenomena reinforce each other and the pop group, starting the performance at 95 dB(A), may be playing at 105-110 dB(A) an hour later, with occasional peaks reaching 120 dB(A).
It has been observed that a noise level of 100 dB(A) may cause a permanent hearing damage, if prolonged, and an exposure to a noise level of 120 dB( A) should not be allowed for more than 30 seconds. Some of the readers may never have attended a pop concert.
To give such readers a better idea of pop concert noise levels, we present in Table 1 the noise levels recorded in Lucknow (Lal, 1984) at various religious and cultural functions. We note from this table that almost all of these are below the noise levels of a pop concert, even at its beginning.
The situation is bad enough, from the view-point of hearing damage, for the music lovers and musicians present at the pop concert. But the matter does not end there, since a far worse problem is created for the neighbours.
A noise level of 95 dB(A) at 9.00 pm may not even be noticed above the TV or radio programmes. But a noise level of 105 dB(A) at midnight will be very disturbing if it can be heard at all. In all probability, such a loud noise will interfere with sleep.
Pop-Music-Induced Hearing Damage:
Since pop music is a fairly recent phenomenon in India and there is not much awareness of the hazards of loud noise, no investigation has been conducted in our country on the hearing damage induced by pop music, to the best of the author’s knowledge.
In Europe and America, however, many such studies have been conducted. We present in this section a typical long-term experimental investigation, conducted in the United Kingdom, on pop-music- induced hearing damage.
These investigations were conducted by Fearn and Hanson (Fearn, 1976, 1981, 1986; Fearn and Hanson, 1984A, 1984B, 1984C) over a period of 12 years. These workers studied hearing damage in school children and young people due to amplified of various relevant parameters such as attendance rate, total number of pop concert attendances, etc. We summarise below some of their main findings.
In addition to attending the live performance at pop concerts, many young people listen to recorded pop music through loudspeakers or headphones. Table 2 shows the percentage of young people in the United Kingdom, in various age groups, listening to recorded pop music through loudspeakers or headphones (Fearn and Handson, 1984A).
Table 3, on the other hand, gives the sound levels at the headphones of a recorder playing pop music for various volume settings. It is evident from this table that prolonged listening to pop music even through the headphones has a high potential for hearing damage.
Table 4 presents the average hearing threshold of 173 attenders of pop music concerts and 91 non-attenders (Fearn and Hanson, 1984B) at various frequencies. The subjects of these studies belonged to the age group 18-25 years and the study was conducted over a period of 12 years.
To appreciate the significance of this study one should keep in mind the fact that, by definition the average hearing threshold of young, healthy, normal subjects should be 0.0 dB(A) Table 4 clearly shows that, except at the frequency of 0.5 kHz, the average hearing threshold of attenders of amplified pop music is higher than that of non-attenders, implying that the attenders have suffered some hearing loss.
Fearn and Hanson (1984B) found that, compared to the average hearing threshold, a much more sensitive parameter to assess the hearing damage is the percentage of subjects with a hearing threshold of 10 dB (A) or more in each group.
This information is presented in Table 5, which clearly shows that, at all frequencies, the percentage of attenders with a hearing threshold of 10 dB (A) or more is higher than that of non-attenders.
Table 6 shows similar data, at the frequencies of 4 and 6 kHz, as a function of attendance rate, while Table 6 presents it as a function of the total no. of attendance of pop music concerts.
The general trends are remarkably clear, in both cases at the frequency of 4 kHz. Both Tables 6 and 7 shows that the percentage of subject with a hearing threshold of 10 dB (A) or more increases at 4 kHz as the attendance rate or the total no. of pop concert attendance increases. These studies of Fearn and Hanson clearly document the hearing damage induced by amplified pop music.