Foam ear plugs

A magstim super rapid stimulator (The Magstim Company New York, NY), which produces a biphasic pulse, coupled with either the figure-8 coil or the H-coil, was used. Prehminary studies showed the H-coil to have a loudness when activated of 122 dB, similar to other cods used in our laboratory. As a standard laboratory practice, subjects were fitted with foam ear plugs to attenuate the sound. 

Figure 20.15 Attenuation characteristics of different hearing protectors (A ear-muffs B piastic foam ear-plugs C acoustic wool ear-plugs)...

Disposable ear-plugs are made from glass down, plastic-coated glass down and polyurethane foam, while re-usable ear plugs are made from semi-rigid plastic or rubber. Re-usable ear-plugs need to be washed frequently. 

Foam plugs—are compressed and twisted between the thumb and forefinger, then inserted into the ear canal. The foam memory then causes the plug to try to return to its original shape, expanding it into the ear canal. The worker s skill in inserting these plugs... 

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