Noise induced hearing loss is cause by exposure to load noises. It doesn't matter how old you are, if you don't protect your hearing, you could lose it and there's no turning back the clock; once yourhearing as gone its gone. A safe sound measures at 85dB or below, but you shouldn't listen to any sounds at or above this level for lengthy periods of time. Whilst exposure to this level of sound shouldn't cause damage to your hearing, it is still recommended to wear hearing protection in situations where there is potential for a suddent rise in the volume, such as city traffic.