Abstract: This invention relates to real time control either in compression or expansion of the amplitude of electrical waves and more specifically to a real time expandor or compressor of the amplitude of sound waves. In general a source of waves which may be the electrical equivalent of a sound including continuous discourse is applied to a plurality of first filters whose output is connected to respective power circuits, that is, circuits that produce at its output a wave whose amplitude is a power, either greater or less than one, of the amplitude of the wave applied to its input. The outputs of the power circuits are applied to respective second filters which are similar to the filters connected to the input of the power circuits and the output of the second filters is connected to a utilization device. Amplifiers may be connected where needed.

Abstract: Apparatus for setting or adjusting an aural prosthesis, such as a hearing aid, in order to provide compensatory amplification or attenuation for aurally handicapped persons such that the prosthesis compensates for the specific auditory deficiencies of that person. The apparatus includes a master hearing aid having one or more adjustable gain controls for determining the person's preferred word discrimination levels for a plurality of frequency bands. As the master hearing aid is set at the person's preferred level for each separate band, a reciprocal control coupled to each master control is adjusted at the same time. A hearing aid is then selected having an acuity deficiency correction characteristic generally similar to that determined by the previous test information, and that hearing aid is coupled to the reciprocal gain controls. The hearing aid selected is of a type which may have one or more adjustable filter networks and a maximum power output adjustment or any combination of one or more of these.

Abstract: A system for testing the hearing of a patient by telephone is disclosed. The patient calls a number, either by touch tone or by dialing, whichever is available, that gives access to the testing equipment. The equipment gives the patient instructions as to how to proceed. The equipment, during the course of the test, applies discrete audio tones at various levels to the phone that the patient is holding to one ear, and records the tones and levels that the patient can hear. The process is repeated for the other ear and this is also recorded. A code number is also recorded so that the test results may be recovered. When the test is complete, the equipment tells the patient what the code number is and that upon payment of a fee the results of the test will be transmitted to him. The equipment may be used in a doctor's or personnel officer's office, in which case the equipment gives the code number, but does not mention a fee.