Browse Prior Art Database

Testing Audio Input and Output Devices for Computers

IP.com Disclosure Number: IPCOM000117603D
Original Publication Date: 1996-Apr-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 125K

Publishing Venue

IBM

Related People

McCall, CD: AUTHOR

Abstract

High quality audio Input/Output (I/O) circuits, microphones, and loudspeakers are becoming standard features of personal computers. During manufacturing, defects may be introduced into these devices which degrade the quality of the signals input to the computer or heard by the user.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 45% of the total text.

Testing Audio Input and Output Devices for Computers

      High quality audio Input/Output (I/O) circuits, microphones,
and loudspeakers are becoming standard features of personal
computers.  During manufacturing, defects may be introduced into
these devices which degrade the quality of the signals input to the
computer or heard by the user.

Present test methods for such devices all suffer from serious
disadvantages:
  1.  Human judgement of audio quality
      o  Subjective
      o  Very difficult in noisy manufacturing environment
  2.  In-circuit testing of components
      o  Requires access to test points in the circuit
      o  Results can not readily be related to the listener's
          experience the defects
      o  Cannot test microphones and loudspeakers
  3.  Instrument-based analysis
      o  Requires dedicated, expensive, signal generators and
          analyzers
      o  These instruments must be regularly calibrated against
          standard signal sources.

The described approach has the following features:
  1.  Applicable to either circuit board or completed box testing.
  2.  'Wrap' testing - that is, generating a signal in the Unit Under
       Test (UUT), sending it out of an output port or speaker,
reading
       the signal in to an input port or microphone, and testing the
       received signal.  Wrap' testing is common practice for other
IO
       devices like communication ports.
  3.  Using the computing power of the UUT to do frequency domain
       analysis of the received signal.  This is the crucial
innovation.
  4.  Averaging of several test runs in the complex frequency domain
       can be used to improve rejection of background noise when
       loudspeakers and microphones are tested in a noisy
manufacturing
       environment.
  5.  Calculating parameters that relate directly to the listener's
       experience - such as signal volume, frequency response,
       background noise and distortion.
  6.  Using arbitrary units of measurement and learning pass/fail
       parameters automatically from measuring a sample of good UUTs
and
       determining limits statistically.

      The described test method uses the processing facilities of the
Unit Under Test (UUT) to analyze the response of the unit to a
specially designed test signal.

      The UUT is assumed to have one or more audio output ports and
one or more audio input ports.  Each input port is connected by a
short cable to one of the output ports.  If the device has a
loudspeaker, a microphone is mounted in a test rig very close to the
loudspeaker and connected to one of the input ports.  If the device
has a microphone, a loudspeaker is similarly mounted and connected to
one of the output ports, through an amplifier if required.  If the
UUT is a circuit board, the wrap...