Acoustic potential energy sensitivity of a zone due to transfer function error

Abstract

Acoustic potential energy is the energy stored in a volume element in case of compression and rarefaction during the acoustic wave propagation. If we control the acoustic potential energy in space, there can be several useful applications such as a personal audio system and therapeutic ultrasound and so on. The focused acoustic potential energy on the biological tissues can ablate a cancer or tumor. Meanwhile, the creation of acoustically focused and defocused regions at the same time can make it possible to realize a sound audible to a user but inaudible to other people, which is called a personal sound. In realizing a personal sound, use of earphones or headphones can be one of the simplest ways to convey a sound personally. However, if it is possible to generate a privately audible zone by using the constructive or de-structive interference of acoustic waves via multiple loudspeakers, then a user can enjoy the sound in more comfortable or safer conditions. In this regard, a number of personal audio systems have been implemented. The desired interference of acoustic waves can be produced by driving a loudspeaker array system with proper control signals, which are designed from the knowledge of transfer functions. The transfer function is the system response between the loudspeaker input and the pressure output, which can be obtained by either exper-imental measurement or mathematical model. However, in many cases, there are differences between the trans-fer function obtained for designing proper control signals and the transfer function of the actually driven loud-speaker array system. The transfer function includes responses of all the electrical or electro-acoustic devices constituting a loud-speaker array as well as the characteristics of acoustic wave propagation in space. Accordingly, various types of errors may be involved in transfer function error and the causes of errors may be also countless. Therefore, It is worth investigating the effect of trans...