8
0
20
40
60
80
100
120
140
160
Threshold Of Audibility
Falling Leaves
Recording Studio
Quiet Apartment
Normal Conversation
"Loud" Office
Power Drill
Threshold Of Pain
Jet Engine
Machinery Hall
Sound-Pressure Level (dB SPL)
Fig. 1.1.: Dynamic range of human hearing
As can be seen, human hearing has a very wide dynamic range of about 130 dB, which surpasses the range
of a DAT or CD player with an approximate range of 96 dB. From a physical point of view, a 6 dB boost
corresponds to an increase in loudness by the factor 2. However, the human ear perceives a signal to be
twice as loud as before only if it is boosted by about 10 dB. This will give you an idea of the variety of sound
manipulations that can be realized with the 24 filters of the FEEDBACK DESTROYER. For each filter, you
can apply a boost of +16 dB or a cut of -48 dB, i.e. you can boost the selected frequency by the subjectively
perceived factor 3 (physically x5) or attenuate it by the factor 27 (physically x250)!
The sound which an EQ produces not only depends on the selected frequency and the amount of gain
(expressed in dB); the bandwidth of the filters also plays an important role. Here, we generally use the so-
called
absolute bandwidth of a filter, which is measured from the lower to the upper cutoff frequency. Starting
from there, you can divide the absolute bandwidth by the filter’s center frequency to calculate the
relative
bandwidth. The
quality factor (Q) is simply the reciprocal value of the relative bandwidth.
0 dB
-2 dB
-4 dB
-6 dB
-8 dB
-10 dB
-12 dB
1 kHz
5 kHz
200 Hz
Bandwidth = 600 Hz
Filter attenuated by 8 dB at 1kHz
Center frequency
= 1 kHz
-3 dB
Fig. 1.2: Typical equalizer filter curve
1. INTRODUCTION
