Study reveals noisy Christmas toys can dama...( take into account the sensitivity of h...)

take into account the sensitivity of human ears to different pitches of sound. It is a logarithmic scale, which means that an increase or decrease of 3 dBA represents a doubling or halving of intensity, the energy it contains. So, for example, 73 dBA is twice as intense as 70 dBA. However, due to the way we hear sounds, a person with normal hearing will only think a sound has doubled in loudness when it is ten times more intense. For example: 80dBA will only sound twice as loud as 70dBA despite actually having ten times as much energy! An average conversation will reach around 60 dBA while a busy street can peak at 80 to 90 dBA.

Generally, exposure to sound levels below 80 dBA are unlikely to cause any hearing damage. Prolonged exposure to sounds over 80 dBA can damage your hearing and the risk increases as the sound level increases. So at 140 dBA noise causes immediate injury to almost any unprotected ear.

Although there are laws about acceptable levels of noise in different situations, it is impossible to set an objective noise level that is safe for all. Provided the ear is allowed ample rest afterwards, a level of 80 dBA might be tolerated for up to 8 hours, but increase that level by just 3 dBA and the time is reduced to just 4 hours. By 95 dBA the tolerance is less than 15 minutes. However, no two people will have an identical tolerance to noise. Research suggests that a genetic predisposition towards hearing loss is an important factor.

How the toys were tested: Toys were measured using a Cel 450 handheld recording SPL meter. Measurements were carried out in a medium-sized carpeted room with background levels below 40 dB(A). Each toy was measured at 2 distances: (1) 2.5cm, simulating close to the ear use and (2) 25cm, simulating normal arm length use. Thirty second recordings were made while the toy was activated and the average equivalent dB(A) was measured along with the peak dB(C) level. Since the cap gun only produ
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Contact: David Reid
david.reid@deafnessresearch.org.uk
44-020-767-98953
Deafness Research UK
11-Dec-2006

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