Hearing aid with digital compression recapture

#The present invention relates generally to audio signal processing. More particularly, it pertains to inhibiting distortions that arise from adjusting gains of preamplifiers and preserving signal compression information for subsequent processing, especially in hearing aids.

#Sound systems can be broken down into three general components: an input device, such as a microphone; a processing system; and an output device, such as a speaker. Sounds are picked up by the microphone, transmitted to the processing system where they are processed, and then projected by the speaker so that the sounds can be heard at an appropriate distance. Both the microphone and the speaker are generally considered to be transducers. One application of the sound system is a hearing aid.

#A transducer is a device that transforms one form of energy into another form of energy. In the case of a microphone, sound energy, which can be detected by the human ear in the range of 20 Hertz to 20,000 Hertz, is transformed into electrical energy in the form of an electrical signal. The electrical signal can then be processed by a processing system. After the signal is processed, the speaker transforms the electrical energy in the electrical signal to sound energy again.

#FIG. 1 is a block diagram of a system according to one embodiment of the invention.

#FIG. 2 is a graph of a signal according to one embodiment of the invention.

#FIG. 3 is a graph of a signal according to one embodiment of the invention.

#In the following detailed description of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown, by way of illustration, specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention.

#The embodiments of the invention focus on inhibiting distortions that arise from automatic adjustments of the gain of preamplifiers in sound systems. An ear-worn hearing aid is an example of such a sound system. As discussed hereinbefore, the automatic gain control, which helps in adjusting the gain of the preamplifier, also hinders by adding undesired distortions to the electrical signal.

#The automatic gain control detects the envelope of the waveform of the electrical signal, compares the envelope to a threshold, and adjusts the gain of the preamplifier. The act of detecting the envelope includes sampling the waveform of the electrical signal to form samples of the envelope that are representative of the magnitude of the waveform. Each sample of the envelope is then compared to the threshold by the act of comparing. If any of the samples is greater than or less than the threshold, the gain of the preamplifier is adjusted by the act of adjusting. After the gain is adjusted, the preamplifier amplifies the electrical signal so as to form an amplified electrical signal.