Apple filed a patent application to the U.S Patent and Trademark Office related to a system that makes the iPhone’s sensors to increase and decrease the volume, as well as switch between the device’s multiple speakers, depending on the distance between the handset and the user.
The patent called “Adjustment of acoustic properties based on proximity detection” describes a method in which data from the iPhone’s proximity sensor is employed to calculate the distance from a user, which is then applied to dynamically adjust the volume level.
The patent covers a number of sensors including cameras and passive light sensors among others. However, the most obvious is the front-facing infrared sensor that is already used to turn the multitouch screen on or off during phone calls. This is not the only sensor it can be used. Any other applicable components can be used with the condition to be able to provide distance data in some embodiments.
The sound adjustment system can easily adjust the volume level based on distance away from the user. The same method can easily be transferred to the speaker, depending on the sound output the user chooses to use.
In some cases, the iPhone will automatically fade from the receiver to the speaker if the distance between the device and the user is reached. In order to make things clear, here is an obvious example. If a user starts a phone call holding its device next to its ear and then puts the device down on a table, the proximity sensor will notice the different and switch to speaker mode.
Moreover, Apple suggests that user profiles can be used in order to implement the proximity-based system. In the same time, the patent calls for frequency and gain adjustment based on proximity and environment, which are controlled by various circuitry arrangements such as filters, amplifiers and audio demultiplexers/splitters.
Since Apple’s iPhone does not have too many buttons, the proximity sensor becomes crucial for initiating phone calls. As a major part for the smart device, Apple also encountered various problems with the sensor responsible for measuring the distance.
When iPhone 4 was launched in June 2010, various customers complained about proximity sensor issues with their devices. Apparently, the sensor would randomly turn the device’s screen on during a call, which led to multiple errant screen touched. The problem was solved with an OS update a few months later.
For now, there is no evidence that Apple plans to use the acoustic system based on proximity sensors on any of its future devices. In the same time, the system might as well be available for the existing models.