Using proximity detection to apply volume ramping of ringing signals & smart vibra
Original Publication Date: 2003-Aug-25
Included in the Prior Art Database: 2003-Aug-25
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Current mobile phones may cause problems when signaling an incoming call. In normal mode there is the risk of "acoustic shock" meaning that if the user has the device near his ear when a call comes in the volume of the ringing signal may be high enough to cause permanent hearing damage. In silent mode on the other hand the user is given notice of an incoming call by a vibrator instead of a sound signal. If the mobile lies on a hard surface like a table it makes the mobile tremble resulting in a very loud noise contradicting the intention of silent mode. For the prevention of acoustic shock it is common practice to introduce a volume ramping in the beginning of the ringing signal which means to lower the volume in the beginning and rising it over some time until normal level giving the user time to take the device away from his ear. More advanced techniques employ a proximity sensor to lower the volume if an obstacle like a human head is detected in front of the mobile. The disadvantage is that the volume is also lowered when there is no risk of causing hearing damage, e.g. when the device is placed in a pocket or front side down on a table, and thus may be too low to be heard. The idea is to combine these two methods. A slow volume ramping from low to high is employed when something is detected in the proximity of the sound outlet (fig. 1). Otherwise the ringing signal is played normally at full volume. In case that the ringing signal is very short using volume ramping in the beginning of the cycle would simply cause the entire cycle of the signal to be played at too low volume. This is solved by ramping over consecutive repetitions of the short ringing signal (fig. 2) so the required sound pressure is reached after some time.