Browse Prior Art Database

Waveform Inversion for Individual Ambient Sound Control

IP.com Disclosure Number: IPCOM000105863D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 125K

Publishing Venue

IBM

Related People

Blalock, JL: AUTHOR [+3]

Abstract

The typical office environment is often noisy. Many computer peripherals such as the fan add noise. Fluorescent lights can also produce annoying distractions. Multi-media microprocessors can be programmed to attenuate many of these common noises for individuals in a room.

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Waveform Inversion for Individual Ambient Sound Control

      The typical office environment is often noisy.  Many computer
peripherals such as the fan add noise.  Fluorescent lights can also
produce annoying distractions.  Multi-media microprocessors can be
programmed to attenuate many of these common noises for individuals
in a room.

     Under user control and adjustment, a TSR
(Terminate-Stay-Resident) program in a multi-processing environment
can:

          1.  Capture a continuous waveform via microphone
          2.  Digitize the analog signal
          3.  Mathematically adjust phase
          4.  Produce a high-fidelity waveform that (for an area near
              the user's ear) will attenuate the office noise sampled

      Refer to Figs. 1-A, 1-B and 1-C, which show an idealized
waveform, its digitization, phase adjustment, and composite results:

          o   Fig.  1-A shows a stylized waveform.  Mathematically,
              any sound wave can be decomposed by Fourier Transforms
              into a combination of simple waves (each defined by
              frequency, amplitude, and phase).  Analog-to-digital

              conversion yields a vector of numbers illustrated below
              Fig. 1-A.  This series of numbers is proportional to
              both the physical pressure of the sound and the voltage
              required to drive a speaker creating that sound.

          o   Fig.  1-B shows another stylized waveform, which
              starting at the same point in time is 180&deg OUT of
              phase.  This also can be digitized as a vector of
              numbers.

          o   Fig.  1-C shows the results (silence) of the
              combination of the waveforms shown in Figs. 1-A and
              1-B.

      This approach can be realized with standard multimedia sound
cards.  Speakers and microphone may be standard commercial
high-fidelity quality.

User Interactions:

          1.  Select an icon starting the following thread of action.
          2.  Use the microphone to capture a short segment (one
              second is adequate) of the sound in question.
          3.  Invoke a Fast Fourier transformation which will
              identify the frequency of the strongest harmonics of
              the digitized waveform.
          4.  Since the distance of the base noise and the computer
              speakers are different (see sample calculations below),
              the user would use a pointing device (such as a mouse)
              to move a pointer on a scroll bar of the icon to change
             ...