Sound and decibels

In short: Sound consists of pressure variations in the air that spread as a wave. Loudness is measured in decibels (dB), a logarithmic scale.

In more detail: An increase of 10 dB is perceived by the ear as roughly twice as loud. Physically that is ten times the sound intensity.

In detail

• Reference values: Whisper about 30 dB, normal conversation 60 dB, road traffic 70 to 80 dB, rock concert over 100 dB.
• Hearing damage: Permanently above 85 dB damages hearing. Ear protection makes sense from that value.
• Frequency: The audible range is roughly between 20 Hz and 20,000 Hz; the upper end shrinks with age.
• Adding levels: Two equally loud sources give only +3 dB, not double.
• Noise protection: Distance, insulation and breaks help more than turning the volume down (echo-und-schallgeschwindigkeit).