Audio Monitor

When monitoring neurophysiological data, experimenters need not be limited to their sense of sight. The data may also be monitored with great sensitivity using the sense of hearing. In such cases, the data are input to an audio monitor and fed to a loudspeaker or a set of headphones. Our ears have evolved to detect subtle patterns of sounds. Neurophysiologists exploit this capability by listening to the electrical signals recorded from the nervous system. Individual action potentials are heard as a popping sound. Simultaneous action potentials from multiple neurons are heard as a whoosh sound. The TREC AUDIO MONITOR is a power amplifier that applies the signal coming from the electrode directly to the speaker or headphones without any delay by data acquisition systems, thereby allowing signals in the audio bandwidth to be heard.

Key features:

  • Monitor channel selction button for 1- out of 16 channels
  • Audio ON/OFF
  • High quality loudspeaker (included)
  • Headphonses jack
  • High quality headphones (included)
  • Rackmountable 19" cabinet
  • Ext. power supply 90-264V AC
  • volume control
  • Noise Threshold control
  • Equalizer control (bass, treble)
Dimensions and Weight: Length (mm): 485 mm
Width (mm): 250mm
Height (mm): 45mm
Weight (kg): 2kg
Power Supply: Mains supply voltage (V): 90-264V AC / 47-63Hz (ext. Power Supply)
Power consumption (W): 5W
Enviromental conditions: Operating temperature range: +10°C to +40°C
Transport temperature range: +10°C to +40°C
Humidity: 20% - 80% RH (non-condensing)
Input data: Number of channels: 1 out of 16
Input connector type: D-SUB 25pin
Output connector type: D-SUB 25pin


The TREC AUDIO MONITOR offers advanced audio features like a noise suppression circuit that allows background noise reduction (e.g. reducing neural background noise while improving the quality of single unit sound). This type of audio monitor is frequently used in central nervous system recording. Each spike is heard as an audible click, and the rate and volume of clicking is a good indicator of nerve cell activity.

Figure 1: TREC Audio Monitor with 1 out of 16 input channels

One use for the TREC AUDIO MONITOR is to listen to the neural signals while stimulating the neurons you can easily determine whether some sounds are correlated to your stimulation. You can then look at the oscilloscope to see whether you can pinpoint the features in the signal that correspond to the sounds you heard thus identifying the relevant activity within the recording. 

Use the volume, bass, and treble controls on the AUDIO MONITOR to adjust the signal level and sound quality; these controls only affect the speakers and will have no effect on the signal that is recorded by the computer. Both speakers of the headphones will deliver the same sound. The Instrument is not intended for clinical measurements using human subjects.

Audio monitors are standard features in TREC neuroscience recording systems. To minimize the potential for aggravation, we include a headphone jack so that users can listen to the audio output without testing the patience of their colleagues.

Once electrodes are in place and the amplifier is turned on and in REC mode, spontaneous action potentials should be evident as fast deflections on the oscilloscope. You should also be hearing ‘pops and crackles’ coming from the audio monitors.

Figure 2: Audio Monitor connection scheme with TREC programmable gain main amplifier PGMA-02