Adjusting for Optimal Volume Levels

The exact steps that need to be taken depend on the exact devices being used, and their device specific setup requirements, and the speech or audio configuration under test. For the simplest case where, for example, a “music” audio file is to be played by a smartphone to a set of Bluetooth speakers, the typical steps would include the following.

1. Choose an audio reference file to be played at DUT1 appropriate for the configuration to be tested.

   The test files are stored on the users computer In the directory "\Frontline <version #>\Development Tools\Audio Expert Test Files\". For example,

   Test_1.03_48kHz_16Bit_3Loops_2Ch.wav

   Note: Reference test files are periodically updated. Shown here is an example. Files delivered with your latest Frontline software version may have changed. Contact Frontline Technical Support for information on the latest reference file versions.

2. Before establishing the Bluetooth connection, play the file while listening to it on the DUT1 device itself, and become familiar with the overall sound quality, generally ignoring exact volume.
3. Set the playback volume at DUT1 to maximum.
4. Set the playback volume at DUT2 to minimum.
5. Establish the Bluetooth connection and begin playback of the file on DUT1, if possible in “Loop” or “Repeat” mode to avoid having to continuously restart.
6. Slowly increase the volume on DUT2 until it is at a comfortable level.
7. If the audio sounds distorted, reduce the playback volume at DUT1, and repeat Step 6.
8. When the clarity of the audio is comparable to that heard when listening to the DUT1 device, proceed with using the Frontline software enabled to capture and analyze the Bluetooth data.
9. Visually observe the waveform in the Audio Expert System Wave Panel comparing it to the image above, "Example: Reference File Waveform, 44.1kHz, 16 bit.". If the level of the -6 dB, 0.9 sec duration, 400 Hz tone (a little over 2/3 of the way through the test) is grossly above or below the –6 dB (50% volume) grid line, adjust the DUT1 volume accordingly and repeat this step. Optimally it would be on or just below the -6 dB gridline, but not above. The peak should never hit the maximum positive or negative limits of the display.
10. Find the “Test ID Found” event in the Event Table to verify that the system has transitioned to Referenced Mode, and verify that the value for “Channel Gain” (or “Level” as implemented in the UI) is within the range of values specified in ""Test ID Found" Event "info1" Maximum and Minimum Values".

If the observed (captured) waveforms do not reasonably conform to the above graphic for Test_1.02, or the “Test ID Found” event is not reported, there is a problem along the audio chain. This could be as simple as a configuration setting, or more subtle such as an encoder/decoder incompatibility.