User manual

Audio Generator

AM700 Audio Measurement Set User Manual

4-11

The following explains the format of an AM700 multitone file:

<Data>

where <Header> is:

am700 multitone <version> <log2bufsize>

<version> is 1.0

<log2bufsize> is the base 2 log of the buffer size in bytes, that is, 10 for

1024, and so on.

<Data> consists of a series of lines, each containing <ToneSpec>. (Each tone is on

its own line.)

<ToneSpec> is

<Freq in Hz> <level in dBV> [<phase in degrees>]

NOTE. The phase parameter is optional. If phase parameters are present for all tones

they will be used for the generated multitone. If phase parameters are missing from

any tone, all tones will get randomized phases.

1. When phases are randomized, this occurs each time the multitone is computed,

Switching to and from multitone will cause a recomputation. This could have a

negative effect on repeatability of very sensitive tests.

2. The same file used for two channels (without setting B to follow A) will

produce different time-domain signals in each channel.

3. To guarantee repeatability you must use the phase parameter. A reasonably

good crest factor results from randomized phases in the interval [0 . . . 360]

degrees.

Once created and edited on a PC, a multitone description file can be copied to the

nvram:/mtone directory on the AM700 using the Storage Manager. For more

information, refer to AM700 Storage Manager on page 4-132.