Choose an earplug of slightly bigger size to avoid whistling. 1 x Hearing Aid. Pocket Hearing aid. Equivalent Input Noise: ≤30 dB. Max Sound Output: 130±4 dB. Max Sound Gain: 50dB. If you hear a howling, check the ear (silica gel) is appropriate and whether the size of plug is tight, the appropriate choice of earplugs and plugged, make sure no air leakage.
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