User manual

Audio Generator

AM700 Audio Measurement Set User Manual

4-13

For example, if you want a multitone signal with 10 tones, a record length of 1024,

at a sampling rate of 48 kHz, the following constraints on tone selection will apply:

Minimum Tone Separation = (48 kHz 1024) X 5

= 234 Hz

Minimum Tone Frequency = (48 kHz  1024) X 3

= 141 Hz

Maximum Tone Frequency < 24 kHz

The two limits that have to be considered in the example are the minimum spacing

and the minimum tone frequency. The number of tones involved does not create

spacing problems, and the maximum tone frequency is limited in this case by the

bandwidth of the high resolution A/D converter rather than sampling frequency.

Using List to Create a Multitone Signal. The AM700 can also create multitones from a

list. A multitone list is created from the same list used to create frequency sweeps.

The List Editor appears in the Generator Control panel as one of the Sweep control

selections. There is one list available for each generator in the AM700; making a

change here also affects the sweep from a list option for the associated generator.

Refer to Sweep List on page 4-21 for more information.

NOTE. When the list is used to generate a multitone test signal, the level setting

for each tone is used only to provide the relative amplitude relationship between

the individual tones. The absolute value of each tone depends on the generator

amplitude setting for the peak value of the multitone test signal.

When you set the generator to multitone and use the list as the source for setting the

included tones in the signal, use the same considerations that are used for selecting

tones as when you create one from a file. The exception is that the record length is

set to 8192 bytes, and you cannot change it. The record length used for list is set to

provide the most flexibility in minimum tone separation and minimum tone

frequency.

For example, with a sampling rate of 48 kHz and a record length of 8192, the

minimum tone separation is 29 Hz and the minimum tone frequency is 18 Hz. The