HEARING AID TONE CONTROL

• US 3,571,514 A
• Filed: 01/07/1969
• Issued: 03/16/1971
• Est. Priority Date: 01/07/1969
• Status: Expired due to Term

• Current Assignee: Kenneth R. Wruk
• Original Assignee: Kenneth R. Wruk
• Inventors: Wruk, Kenneth R.
• Application Number:
  US04/789,581
• Time in Patent Office: 798 Days
• US Class Current: 381/320
• CPC Class Codes: H03G 5/12 incorporating negative feedback
• CPC Class Codes: H04R 25/502 using analog signal processing

Abstract

A tone control circuit for a transistorized hearing aid amplifier comprising a transistor amplifier stage with an electromagnetic hearing aid microphone connected to its input. The output has a resistor connected thereto for establishing the operating point of the stage. A switch is provided for connecting a second resistor and a capacitor in parallel with the first resistor to change the operating point of the transistor in such a manner as to lower the input impedance of the transistor. The decrease in input impedance reduces the high frequency response of the microphone-transistor combination and thereby provides treble tone control action.

Claims

1. A tone-controlled hearing aid amplifier comprising:

an amplifier device of the type comprising an input electrode and an output electrode and having a predetermined inputsignal-to-output-signal amplifying characteristic and having an input impedance which varies with variations in the operating point on said characteristic;

an electromechanical transducer, including a magnetic hearing aid microphone responsive to ambient audio sound waves and having a frequency response range which is narrow relative to that of said amplifier device, coupled to said input electrode;

means including a load impedance coupled to said output electrode for establishing a predetermined operating point for said device, whereby audio frequency signals developed by said transducer are amplified by said device and an amplified output signal is produced at said output electrode;

an output transducer coupled to said output electrode for converting said amplified output signal into intelligible audio information at a power level higher than that of said ambient waves; and

tone control means including a resistor, a capacitor, and a switch operable to simultaneously connect said resistor in parallel with said load impedance and said capacitor from said output electrode to said input electrode, thereby decreasing said input impedance and providing treble frequency attenuation of greater than 6 decibels per octave with a single reactive component.