User manual

Audio Generator
4-12
AM700 Audio Measurement Set User Manual
To select a multitone description file, in the Waveform Control screen, touch the
Filename soft key and turn the knob to select the file. Then, touch the Select soft
key to accept the selected file. Touch the File soft key to direct the audio generator
to the multitone description file as the source for generating multitone signals.
Rules for Constructing a Detectable Multitone Signal. Constructing a multitone signal
for reliable FFT Multitone detection by the AM700 is based on tone separation,
sampling rate, and record length. How many tones you use in constructing the signal
is limited by the constraints of the minimum spacing of the tones as determined in
the following text. How low or high a frequency you can use is also constrained.
Things to consider when constructing a multitone signal file are:
H Record lengths are in powers of 2 and the following lengths can be specified in
the multitone file.
2
9
- 512, 2
10
- 1024, 2
11
- 2048, 2
12
- 4096, and 2
13
- 8192 bytes.
H Sampling rates are different in each of the three acquisition systems.
High Resolution Mode 48 kHz
High Bandwidth Mode 192 kHz
AES Digital Input 32, 44.1, or 48 kHz
H Each component of a multitone signal should be separated from the adjacent
components by an amount based on the following formula:
Minimum Tone Separation in Hz = (Sampling Rate  Record Size) X 5
H The lowest tone that can be reliably recognized is equal to or greater than that
determined by the following formula:
Minimum Tone Frequency in Hz = (Sampling Rate  Record Size) X 3
H The highest tone that can be reliably recognized in based on the sampling rate.
Tones approaching half the sampling frequency will be incorrectly sampled.