Monday, August 14, 2017

Optimum Noise levels for class room teaching

Everyday exposure to noise over time has an impact upon our ability to hear and on the degree of hearing loss that develops. Continuous exposure to sounds above 85 db can cause progressive hearing loss.  Noise-induced hearing loss is the most common and obvious outcome of noise pollution. It is also an important occupational health concern due to high workplace noise levels. However, noise pollution has also been associated with other health problems such as stress, anxiety, high blood pressure, increases heart rate, heart disease. It may manifest as disturbed sleep/ insomnia, headache, fatigue, irritability, loss of concentration and decreased work efficiency.

Noise levels are also an increasing concern in class rooms. The source of noise can be external such as street traffic, playground noise, airplanes, etc. The source of noise can be indoor, such as hallway noises, noise from other rooms etc. or noise within the classroom itself such as conversation, noise from fans, lights, paper, etc. Noise in a class room is not conducive to learning. Background noise in classrooms interferes with auditory communication and adversely affects speech perception and speech recognition. It interferes with language and reading development and hampers academic performance. Attention and memory are also adversely affected.

Speech intelligibility or understanding is determined by the signal to noise ratio, which should be at least 15dB i.e. the teacher should speak at least 15 db louder than the noise in the classroom for the student to optimally comprehend what he/she is hearing. For clear speech perception the background noise levels should not exceed 35 dB in schools as recommended by the WHO. The reverberation time in the classroom should be about 0.6 sec. Reverberation time is the length of time required for sound to decay 60 db from its initial level in a room. A longer reverberation time together with background noise increases noise levels and makes speech perception even more difficult.

Hospitals are noisy and high stress work environment places.

Because of high background noise, such as in emergency dept. and OTs, the conversation has to be conducted at higher dbs for clear speech communication (normal conversation is between 60-70 db).

Noise can interfere with oral communication leading to mediation errors as a result of orders that are misunderstood.

A noisy environment affects performance of any complex task in a hospital as it reduces concentration. It has been shown that “mental activities requiring a lot of working memory, such as paying attention to a variety of different cues or performing a complex analysis, are especially noise-sensitive”. Failure to hear a warning signal or alarm over the general background noise in an ICU may have potentially catastrophic outcome.

Noise affects effectiveness of health care. Hence, hospitals too should have similar noise levels as educational institutes.

Schools and hospitals are “silence zones”. Silence zone is an area comprising not less than 100 m around hospitals, educational institutions, courts, religious places or any other area as per the Noise Pollution (Regulation and Control) Rules, 2000.

Every effort should be made to reduce noise levels in hospitals for optimum delivery of health care.

Dr KK Aggarwal

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