Triggered Record Using WAV File

The purpose of this sequence is to demonstrate SoundCheck’s Triggered Record – Frequency Trigger function which allows you to test the output of devices without analog inputs such as tablets, cellphones and MP3 players. A stimulus WAV file is created in SoundCheck and transferred to the device under test, where it is played back and the response recorded in SoundCheck as if the stimulus were played directly from SoundCheck. The Acquisition step is triggered by the 1 kHz pilot tone in the stimulus file. Frequency triggers are more robust than level triggers which are susceptible to false triggering due to background noise.

The stimulus WAV file to be used on the device under test (DUT) may be customized in the Stimulus step. The stimulus default is an R40 stepped sine sweep from 20 kHz to 100 Hz, prepended with a 250 ms 1 kHz pilot tone which is used to activate the frequency trigger. The stimulus can be saved as a WAV when the sequence is run. The WAV will have the same sample rate and bit depth as set in your system Hardware configuration. By default, the WAV file is automatically normalized to 0 dB FS in the autosave step, so the stimulus level is not important.

• The parameters of the sweep in the stimulus step are used when creating the WAV file. The duration of this stimulus must be considered in the “Time” field of the acquisition step. See page 2.
• The stimulus step must remain in the sequence and the stimulus settings cannot be changed without re-saving the stimulus WAV file.
• The stimulus WAV file used in this example is included in the sequence folder.
• Changing the sample rate or bit depth in the hardware configuration also requires re-saving the WAV file.

Acquisition Step Settings

Mode: Record

Record Type: Triggered

Time (sec): Default=3 sec. Must be set to slightly longer than length of original stimulus sweep plus the Trig. Offset value

Input Channel: Set to Reference Mic

Trigger Type: Level & Frequency

Trigger Level: Default=80 dB. Should be set relative to the desired playback level from DUT

Auto: Enabled, (will auto detect trigger frequency). When disabled, allows for user defined trigger frequency

Trigger Unit: Default=dB.  Can be set to dB or Pa according to user preference

Trigger Signal Path: Reference Mic

Trigger Offset (sec): Default=-50ms. Sets the amount of time that the Acquired Signal is shifted, relative to the point at which it is triggered.

Slope: For triggering on WAV files this should be set to positive

Time Out (sec): Amount of time the step will wait to trigger before continuing to the next step

The waveform window in the final display shows the stimulus waveform as well as the recorded time waveform. This display can be used to make sure the stimulus is well within the start and stop time of the acquisition step.

Also displayed are the Fundamental, H2, H3, THD, Rub & Buzz and Perceptual Rub & Buzz.

Jitter and playback sample rate of the DUT are in the Memory List Values Tab and can also be displayed.