Abstract: A composite sound dampening structure includes a first base layer of sound dampening material extending around and against an inside surface of a container and a second wedge layer of sound dampening material attached to an inside surface of the first base layer. The composite sound dampening structure provides improved acoustic dampening in relative small sound chambers. An audio test system generates a composite audio signal of multiple different audio signals that are combined together using linear superposition. The composite audio signal allows a device to be simultaneously tested with multiple different audio frequencies.

Abstract: A composite sound dampening structure includes a first base layer of sound dampening material extending around and against an inside surface of a container and a second wedge layer of sound dampening material attached to an inside surface of the first base layer. The composite sound dampening structure provides improved acoustic dampening in relative small sound chambers. An audio test system generates a composite audio signal of multiple different audio signals that are combined together using linear superposition. The composite audio signal allows a device to be simultaneously tested with multiple different audio frequencies.

Abstract: A composite sound dampening structure includes a first base layer of sound dampening material extending around and against an inside surface of a container and a second wedge layer of sound dampening material attached to an inside surface of the first base layer. The composite sound dampening structure provides improved acoustic dampening in relative small sound chambers. An audio test system generates a composite audio signal of multiple different audio signals that are combined together using linear superposition. The composite audio signal allows a device to be simultaneously tested with multiple different audio frequencies.

Abstract: An automatic testing system for electric nerve stimulator units is described wherein a digital computer controller utilizing programmable read only memory is used to control testing transcutaneous electrical nerve stimulator (TENS) units, such tests being conducted by sensing the output pulses from the stimulator under test and processing the output pulse signal information by circuit means under the control of the computer resulting in digital readouts of the peak output voltage, width and rate of the output pulses of the stimulator. The load impedance and quantity of delivered pulse charge for a patient can also be determined as digital readouts and indications of the pulse polarity and/or bipolarity is displayed.

Abstract: An automatic transient response analyzer system takes advantage of a digital computer and circuitry controlled thereby to measure the time that a device under test takes to come within specified limits of a final output when driven by a signal which stepwise increases or decreases in amplitude by a known amount.

Abstract: A microphone coupler for use in performing frequency response tests on earphones of a type normally used for testing the range and condition of human hearing in which a microphone is sealingly carried. The microphone coupler is adapted to rest in position on the earphone under test and is coupled thereto with the proper force by virtue of its own weight, and it includes lip means for guiding the microphone coupler into concentric engagement between a cushion-engaging surface and an earphone to be tested with the lip means also protecting the cushion-engaging surface.

Abstract: A battery charging circuit limits the charging current to one or more series connected cells such that the cells do not receive a damaging overcharge if not removed from the circuit after the rated charging time. A first transistor shunts the battery when the voltage thereof reaches a certain level. Temperature compensation means corresponding with the change in battery voltage with temperature is provided by the base-emitter path of a second transistor connected between biasing means and the shunt transistor.