A mobile communication apparatus, an accessory device, and a method for adjusting one physical property of an acoustic signal, wherein the apparatus includes a ringtone generator adapted to generate the acoustic signal, an ultrasound receiver apt to receive an ultrasonic signal, and a processor configured for detecting at least a physical parameter and/or a content of the ultrasonic signal, determining, on the basis of the at least one physical parameter and/or content of the ultrasonic signal, attenuation information that can quantify the attenuation suffered by the ultrasonic signal and/or the acoustic signal, determining, on the basis of the attenuation information, the physical property of the acoustic signal to be generated, and generating the acoustic signal having the determined property, so that the probability to hear the acoustic signal increases.