Audio metrics for head-related transfer function (HRTF) selection or adaptation

A device, comprising:

• a memory configured to store a plurality of head-related transfer functions (HRTFs), each of the HRTFs being associated with a different head size;
• and
• a processor configured to:
• receive time-related information associated with detecting a sound at a first microphone coupled to or located near a user's left ear,
• receive time-related information associated with detecting the sound at a second microphone coupled to or located near the user's right ear,
• determine a time difference between detection of the sound at the first microphone and detection of the sound at the second microphone,
• estimate a user's head size based on the time difference,
• at least one of a) identify a first HRTF associated with the user's head size, b) generate a first HRTF based on the user's head size, or c) modify an existing HRTF to provide a first HRTF based on the user's head size, and
• apply the first HRTF to audio signals to produce output signals;
• and
• a communication interface configured to forward the output signals to first and second speakers configured to provide sound to the user's left and right ears.

A system, comprising:

• a headset comprising:
• a right ear speaker,
• a left ear speaker,
• a first microphone coupled to the right ear speaker, and
• a second microphone coupled to the left ear speaker;
• and
• a user device configured to:
• estimate a head size of a user wearing the headset based on a time difference associated with detection of sound received by the first and second microphones, and
• identify a head related transfer function (HRTF) to apply to audio signals provided to the right ear speaker and left ear speaker.