Monitor Instruments, Inc.
Monitor Instruments, Inc. is a manufacturer of industrial audiometers and audiometric accessories, offering quality instruments and professional calibration services for audiometers and acoustic safety equipment since the early 1970's.
(800) 853-6785  ·  (919) 732-5400  ·  FAX (919) 732-6153  ·
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 ANM-2 screen

The ANM-2 Ambient Noise Monitor

What are the background noise levels in your audiometric test environment?

The ANM-2 ambient noise monitor displays the levels in real time, in real numbers, at octave bands as required by OSHA. 125 Hz and 250 Hz octaves are optional.

When connected to a Microsoft Windows®-based computer via an available USB port, the ANM-2 becomes a Type 2 Sound Level Meter with a Class II Octave Band Filter.

This system allows the operator to plug the microphone directly into the ANM-2 module when testing in an office environment or place the microphone inside a sound booth and patch it through to the ANM-2 module outside the booth. Either way, the noise levels in the test environment are sampled continuously and fed back to the operator via the computer display.

Results are displayed in a small (approximately 2" x 3") display and control panel as shown in the screenshot (right). Levels are updated each second, and thresholds exceeding predetermined limits are highlighted.

The system can also be set to alert the operator visually or audibly only when limits are exceeded. This allows the control panel to be minimized, and hidden from the computer display.

Microphone Options

The ANM-2 is available with either an economy or professional class microphone. The economy microphone is adequate for OSHA compliance, with a noise floor at approximately 30 dB at 500 and 1000 Hz, while the professional class microphone has a noise floor of approximately 9-12 dB at 500 and 1000 Hz.

The microphones are completely interchangeable, though a recalibration with a sound calibrator is required when changing from one microphone type to another.

Features and Benefits

  • Visual or Audible operator alerts when thresholds are exceeded
  • Accessible internal relay triggered when thresholds are exceeded
  • OSHA- or operator-defined thresholds
  • 125 and 250 Hz octaves optional
  • Calibration adjustments performed using standard 1000 Hz sound calibrators
  • Capable of logging noise level measurements
  • Consumes very few computer resources
  • Small and unobtrusive
  • Durable microphone and ANM-2 module
  • Very economical
  • Powered from USB cable, batteries not required
  • Noise level certification printed out at a click of a button

Standard Equipment

  • ANM-2 module
  • Microphone (Economy or Professional class)
  • Microphone desk stand
  • Mounting bracket
  • Microphone cable
  • Patch cable
  • USB cable
  • Software disk
  • Operator manual


  • Meets ANSI S1.4 Type 2, Type S (Special Applications) for Sound Level Meters
  • Meets ANSI S1.1.11 for Octave Band Filters
  • Frequency range: 88 Hz to 11.312 kHz. (Octave bands from 125 Hz to 8000 kHz)
  • Measurement range (typical) at 1000Hz:
    — Economy class microphone: 28dB to 85dB
    — Professional class microphone: 10 dB to 60dB
  • Calibration levels: 94.0 to 114.0dB at 1000Hz only
  • Frequency weighting: Linear with Octave Band only
  • Microphone size: ½ inch, economy and professional class
  • Display resolution: 0.1dB
  • Power requirements: USB powered
  • Auxiliary relay contacts: Maximum current 2 amps and 30 volts


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