| Android Audio Quality Verifier App |
| ================================== |
| |
| This app runs a set of audio quality tests on an Android device, |
| to verify the end-end sound recording path. |
| |
| If any of these tests fail, the device is probably unsuitable |
| for demanding audio tasks such as speech recognition. |
| If all the tests pass, the device audio is of a good standard. |
| Note that not all possible audio defects can be detected by this |
| test suite, so passing does not guarantee ideal audio quality. |
| |
| Hardware setup |
| -------------- |
| |
| The required physical set-up consists of a powered speaker, |
| connected to the Android's headphone output by a standard |
| audio cable. |
| |
| For loudspeakers which come in pairs, you only need to use |
| one speaker (typically the powered or master speaker); you |
| can leave the second speaker disconnected. |
| If the speakers are stereo within a single unit (sometimes |
| with speakers facing in opposite directions), place the phone |
| in front of either of them. |
| Speakers with multiple drivers per channel (e.g. a tweeter |
| and a woofer) are not suitable. |
| |
| The phone should be placed in front of the centre of the |
| speaker cone. The distance from the speaker will be adjusted |
| during calibration; typically you could expect it to be around |
| 3cm or so. |
| Use a supporting platform such as a stack of books to raise |
| the phone to the correct height to line up with the speaker. |
| |
| Bluetooth connection is possible but cable connection is |
| usually preferable. |
| |
| Recommended loudspeakers |
| ------------------------ |
| |
| Using suitable loudspeakers ensures that test failures highlight |
| problems with the Android device under test, and not limitations |
| of the loudspeakers. The following loudspeakers work well for this |
| purpose: |
| |
| 1. Yamaha NX-B02 |
| |
| Use on AC power, not batteries. |
| This speaker works well with Bluetooth as well as a wired connection. |
| Note that it's not uncommon for the devices to exhibit different |
| bugs under Bluetooth. |
| |
| 2. Cakewalk MA-7A (Edirol / Roland) |
| |
| The "Bass Enhancer" feature MUST be switched off. |
| Note that it turns itself on again every time the speakers are |
| powered on, so it is easy to forget to switch it off! |
| |
| Software setup |
| -------------- |
| |
| 1. Build the application's apk. |
| 2. Install the apk using adb. |
| 3. Run the app. |
| 4. Click "Calibrate". Position the phone as described in |
| Hardware setup above, with the microphone facing the speaker, |
| and adjust the volume of the speaker until the status message |
| indicates it is correct. |
| 5. Click on any test in the list to run it, or "Run All" to run |
| each test in sequence. |
| 6. Click "Results" to view the outcomes. A correctly functioning |
| device should pass all tests. |
| 7. Click "Send by email" from the results page to send the |
| results to an e-mail address of your choice. The recordings |
| made are also attached as raw 16 bit, 16 kHz audio files to |
| help you diagnose any failed tests. |
| |
| Q&A |
| --- |
| |
| Q. What if the sound level check fails? |
| A. Go back to the calibration step before running any other test. |
| Make sure the device has not been moved. |
| We also recommend that once the setup is calibrated there are no |
| moving objects or people near the device under test, since these |
| will change the acoustic properties of the environment from the |
| calibrated state. |
| |
| Q. Some of the tests sound very loud. Is this normal? |
| A. The clipping test will generally be very loud indeed; |
| the others should be at a moderate volume. |
| |
| Q. What sort of room should the tests be performed in? |
| A. Any, as long as the background noise levels are kept low, to |
| avoid interference with the test recordings. |