Apple Soundtrack Pro - Manual (Page 200)

200 Chapter 9 Working With Audio Effects
Note: The frequencies shown for each range are approximate. Any division of sound
into frequency ranges is somewhat arbitrary, and is meant only to give a general
indication of each range.
Roll-Off Filters
The simplest types of EQ effects are roll-off filters, which include lowpass, highpass,
bandpass, and shelf filters. Lowpass filters affect all frequencies above a specific
frequency, called the cutoff frequency. Frequencies above the cutoff are attenuated or
“rolled off” gradually, usually by a fixed number of decibels per octave. Highpass filters,
by contrast, affect all frequencies below their cutoff frequency. Bandpass filters exclude
all frequencies close to their center frequency. You can set the center frequency, and also
set the bandwidth or Q, which specifies how wide a range of frequencies around the
center frequency are affected.
These EQs include parameters for setting the cutoff frequency. Shelf filters add
parameters to control the gain (the amount of boost or cut). You can use roll-off filters
as “broad brush” effects to boost or cut a large range of frequencies.
Bass 50–250 Hz Corresponds roughly to the bass
tone control on a stereo.
Includes the fundamental
frequencies of voices and of
musical instruments. Excessive
boosting in this range can
sound boomy and thick.
Low Bass 50 Hz and below Also called sub bass. Very little of
the sound of voices or musical
instruments falls in this range.
Many sound effects used in
movies, such as explosions and
earthquakes, fall in this range.
Name Frequency range Description