When designing a handset for use in mobile telephony, handset designers generally start with an ear model. Additionally, handset designers typically pay close attention to the requirements of the mobile telephone network operators (carriers) that will market and sell the handsets. Currently, carriers require that handsets be designed based on either a “high-leak” ear model or a “low-leak” ear model. In the high-leak ear model, an attempt at forming a seal between a mobile telephone handset and a user's ear is expected to form a consistent seal that has a significant acoustic leak. In the low-leak ear model, an attempt at forming a seal between a mobile telephone handset and a user's ear is expected to form a consistent seal that has insignificant acoustic leak.
A user of that handset may change the position of their ear relative to the handset, and subsequently the acoustic leak, throughout a phone call or based on personal holding position. Also, each user has a different acoustic load due to variations in ear size and shape; accordingly, the user may prefer a lower leak design or a higher leak design.
Tuning a handset often involves creating an optimum acoustic equalizer (EQ) setting. An acoustic EQ setting determines which frequencies of received audio are amplified, and to what extent, before the received audio is sent to a handset speaker, and, potentially, which frequencies are suppressed, and to what extent. The goal is to meet a specific “frequency-versus-level mask”. Such masks are determined by standards bodies, such as The 3rd Generation Partnership Project (3GPP, see www.3gpp.org).
However, during operation, users are often unable to form a consistent seal between the ear and the handset, due to movement and changes in position during the voice call. The amount of acoustic leak from the seal is dependent on the manner in which the handset is held by the user and the size and shape of the user's ear. Under those circumstances wherein the user forms a low-leak seal and the handset has been designed with a single acoustic EQ setting that assumes a high-leak seal, the user may complain about poor audio quality. For example, the user may complain that received audio sounds “boomy” or “muddy”. Given the variety of user ear shapes and sizes, along with the variety of manners in which users hold the handset, it may be quite difficult to establish a single acoustic EQ setting that will meet the requirements of all users and certification bodies.