Run audio framework CTS Verifier tests

The audio framework CTS-V tests require human intervention and some external hardware, including an audio loopback dongle, a USB-to-analog adapter or interface, a USB reference microphone, and external speakers.

To access the tests on this page, see General instructions.

Loopback latency test

The audio loopback latency test measures the total time from the generation of an audio signal to the detection of that same signal. This time measurement is used as a proxy for measuring the overall latency of the audio system.

The latency is measured over several data paths, including:

• Speaker to microphone
• USB audio output to input
• 3.5 mm analog output to input if the device supports it

Select peripherals

If the device has a 3.5 mm analog headset jack, you need an audio loopback dongle or plug. The dongle contains electronics that route an audio output signal back to the audio input.

Figure 1. Audio loopback plug.

For testing USB, you have two options. The first option is to use an audio loopback dongle connected to a USB-to-analog adapter, shown in the following figure:

Figure 2. Audio loopback plug connected to USB-to-analog adapter.

The second option is to use a USB audio interface with cables that connect the output to the input.

These instructions are for the Presonus AudioBox USB 96 device:

1. Connect the Input 1 connector to Main Out L.
2. Connect the Input 2 connector to Main Out R.
3. Set the Input 1 knob to straight up.
4. Set the Input 2 knob to straight up.
5. Set the Phones knob to 0.
6. Set the Mixer knob to the far right for Playback.

7. Set the Main knob to about 45 degrees left of straight up (about 10:30 on a clock face).

   

   Figure 3. USB audio interface with the correct settings.

   

   Figure 4. USB audio interface top view with the correct connections.

Run the audio loopback latency test

After setting up your selected peripherals, run the audio loopback latency test to take measurements for the loopback latency on all paths supported by the device under test (DUT):

1. Test the internal speaker to the internal microphone (speaker or mic route):

   • Perform this test in a quiet room.
   • Place the DUT flat on a table. If the DUT is in a case, you might need to remove that case.
   • Tap Start for the speaker or mic route. A series of noise bursts play, and at the end of the test process the results for the speaker or mic route display. You might need to adjust the volume to get a sufficient confidence value.

2. If the DUT doesn't have an analog headset jack, skip this step. Otherwise, test the analog headset jack:

   • Insert the loopback plug into the analog headset jack on the DUT. This activates the Start button for this route.
   • Tap Start. The same series of noise bursts is routed through the headset jack and the latency is measured. You might need to adjust the volume to obtain a sufficient confidence value.

3. If the DUT doesn't have a USB port that implements USB host mode, skip this step. Otherwise, test the USB port:

   • Connect the USB loopback device (adapter and loopback plug OR USB interface with appropriate loopback cables) to the DUT.
   • Tap Start. The same series of noise bursts are routed through the USB adapter or interface and the latency is measured. You might need to adjust the volume to obtain a sufficient confidence value.

4. Report the results:

   • If all routes meet the criteria listed in the Android CDD, mark the test as passed.
   • If any route doesn't meet the criteria, mark the test as failed.

Execute the audio frequency line test

This test uses an audio loopback dongle to characterize the left and right line audio output from the 3.5 mm analog jack. The test uses the mic feedback from the plug to capture audio and compute a frequency response for each channel.

A criterion for minimum energy expected in each band (out of four) is applied for each channel.

To run this test:

1. Follow the General instructions to access the test.

2. Tap Yes or No to report whether the device has a physical headset port. If it doesn't have a physical port, mark the test as passed by tapping the green checkmark at the bottom of the screen.

   

   Figure 5. Audio frequency line.

3. Connect a loopback plug to the headset connector (see Loopback latency test).

4. Tap Loopback Plug Ready.

   

   Figure 6. Loopback plug ready.

5. Tap Test and wait for the test to complete.

6. When the test is complete, view the results on the test screen.

   

   Figure 7. Testing complete.

7. If the test passed, tap the green checkmark. If the test failed, tap !.

Run the audio frequency speaker test

This test uses the signal captured by an external USB reference microphone to assess the speakers' frequency response.

A reference microphone delivers a flat, uncolored audio response. These microphones are often used for analysis and measurement equipment.

Minimum recommended reference microphone characteristics:

• Flat frequency response on range 100 Hz to 20 kHz: +/- 2 dB S/N ratio 70 dB (A-weighted)
• THD ratio @ 1000 Hz less than 1% at 127 dB SPL

Recommended microphones include the miniDSP USB measurement calibrated microphone and the Dayton Audio UMM-6 USB measurement microphone.

To run the test:

1. Tap Yes or No to report whether the DUT supports a connection of a USB reference microphone. If it doesn't, mark the test as passed by tapping the green checkmark at the bottom of the screen.

   

   Figure 8. Support USB microphone.

2. Connect a USB reference microphone to the DUT and place the microphone 20 cm away from the DUT and perpendicular to the center of the screen:

   

   Figure 9. Device under test.

3. Tap USB Reference microphone ready.

   

   Figure 10. Microphone ready.

4. Tap Test and wait for the test to complete.

5. When the test is complete, view the results on the test screen.

6. If the test passed, tap the green checkmark. If the test failed, tap !.

Execute the audio frequency microphone test

This test requires both external speakers for a white noise sound source and a USB reference microphone to calibrate the DUT's internal microphone against. The speakers don't need to have a flat frequency response, but they need good coverage from low frequencies (100 Hz) to high frequencies (20 kHz).

To run the test:

1. Report whether the DUT has a physical audio output port. If it doesn't, mark the test as passed by tapping the green checkmark at the bottom of the screen.

   

   Figure 11. Audio microphone test.

2. Position the speakers 40 cm perpendicular to the center of the screen of the DUT.

   

   Figure 12. Device under test.

3. Connect external speakers to the auxiliary phone using the headphone or line out connector. Unplug any USB microphone connected to the DUT.

4. Tap Play on the auxiliary phone, tap Test on the DUT, and wait for the test to complete.

   Figure 13. Test noise.

5. Connect a USB reference microphone to the DUT. Keep the external speakers connected and position the microphone next to the DUT's internal microphone, pointed toward the external speakers.

   

   Figure 14. Device position.

   

   Figure 15. Microphone position.

6. Tap Test on the DUT to test USB background and wait for the test to complete.

   

   Figure 16. Test USB background.

7. Tap Play on the auxiliary phone, tap Test on the DUT, and wait for the test to complete.

   

   Figure 17. Test USB noise.

8. Record the test results.

Run the audio frequency unprocessed test and voice recognition test

This test requires a sound pressure level (SPL) meter in addition to a USB reference microphone and external speakers.

For the frequency unprocessed test, if the DUT has a definition for the Audio Frequency Unprocessed feature, all sections of this test must pass. If the DUT doesn't define this feature, the test can pass even if some sections fail.

To run the test:

1. Connect external speakers to the auxiliary phone. Unplug any USB microphone connected to the DUT.

2. To conduct the tone test:

   1. Tap Play on the auxiliary phone.

   2. Move the SPL meter back and forth in a straight line from the speakers until it detects a sound pressure level of 94 dB SPL for the frequency unprocessed test and 90 dB SPL for the frequency voice recognition test. The following figures illustrate the sound pressure level, which is shown on the sound pressure level meter located on the far left.

      

      Figure 18. Test tone setup for preset unprocessed.

      

      Figure 19. Test tone setup for preset voice recognition.

   3. Move the DUT and place the microphone in about the same location found in the previous step.

      

      Figure 20. SPL meter placement.

   4. Tap Play on the auxiliary phone.

   5. Tap Test on the DUT. The DUT performs a short audio capture.

      

      Figure 21. Audio capture.

3. To conduct the noise test:

   1. Position the speakers perpendicular to the center of the screen of the DUT and 40 cm away.

      

      Figure 22. Speaker placement.

   2. Tap Play on the auxiliary phone.

   3. Tap Test on the DUT and wait for the test to complete.

      

      Figure 23. Running test.

4. To test USB background:

   1. Connect a USB Reference microphone to the DUT and position it close to the DUT's internal microphone.

   2. Tap Test. The test runs and displays results on screen.

      

      Figure 24. Running test.

5. To test USB noise:

   1. Place a USB microphone in the same position as in the previous test.
   2. Tap Play on the auxiliary phone. The speaker plays broadband noise.

   3. Tap Test on the DUT. The test runs and displays results on screen.

      

      Figure 25. Running test.

6. View the results for all four sections of the test. Repeat sections as needed.

   

   Figure 26. Test results.

7. If the test passed, tap the green checkmark. If the test failed, tap !.