Game Development Reference
In-Depth Information
Table 13.1 Decibel Levels for Different Sounds
dB Level
Description
0
The softest sound a person can hear with normal hearing
10
Normal breathing
20
Whispering at five feet
30
Soft whisper
50
Rainfall
60
Normal conversation
110
Shouting in ear
120
Thunder
150
Mr. Mike screaming when he beats his nephew Chris at
Guitar Hero
The reason the scale is a logarithmic one has to do with the sensitivity of your ears.
Normal human hearing can detect sounds over an amazing range of intensity, with
the lowest being near silence and the highest being something that falls just shy of
blowing your eardrums out of your head. The power difference between the two is
over one million times. Since the range is so great, it is convenient to use a nonlinear,
logarithmic scale to measure the intensity of sound.
Did you ever wonder why the volume knob on expensive audio gear is marked with
negative dB? This is because volume is actually attenuation, or the level of change of
the base level of a sound. Decibels measure relative sound intensity, not absolute
intensity, which means that negative decibels measure the amount of sound reduc-
tion. Turning the volume to 3dB lower than the current setting reduces the power
to your speakers by half. Given that, and I can put this in writing, all the stereo
heads out there will be happy to know that if you set your volume level to 0dB,
you
ll be hearing the sound at the level intended by the audio engineer. This is, of
course, usually loud enough to get complaints from your neighbors.
'
If you happen to have some speakers with the cones exposed, like my nice Boston
Acoustics setup, you can watch these cones move in and out in a blur when you
crank the music. It turns out that the speakers are moving in correlation to the plot
of the sound wave recorded in the studio.
