Apple notes that when properly seated in a user's ear, earbuds should form a seal. This allows music to be played back with satisfactory performance. However, poor seals can degrade the sound quality and affect the volume level. Apple sees this as an opportunity for improvement.
Audio performance may be affected by the degree to which the earbuds form seals with the user's ears. To compensate for potential variations in seal quality, seal quality measurements may be made during use of the earbuds and appropriate actions taken. Control circuitry in an electronic device may be used to generate audio output signals during media playback operations. The control circuitry may also generate test signals such as sine wave test tones. Communications circuitry in the control circuitry of the electronic device may communicate with corresponding communications circuitry in control circuitry located in an attached headset.
Seal quality measurements may be made using speaker impedance measurements. With this type of arrangement, the control circuitry of the electronic device and headset may be used to apply signals to the speakers of the earbud while monitoring speaker currents. The signals that are applied to the earbud speakers may be test tones. While applying the test tones, speaker current measurements may be made using a current sensing resistor. Speaker current measurements may also be made by monitoring speaker current flow using a secondary speaker coil and associated current sensing circuitry.
In response to these measurements, Apple could generate informative messages for the user, increasing overall earbud volume, correcting mismatched balance between left and right earbuds, adjusting equalization settings, and make adjustments to noise cancellation circuitry.
The full patent details can be found at the link below...
Read More [via AppleInsider]