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How To: Reduce Noise Output from a Brushed Motor April 19, 2012

Posted by Servo2Go.com in Technical Support Information.
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Pittman's Brush DC Motor Family

Pittman's Brush DC Motor Family

Noise is often the single toughest challenge faced by design engineers when developing products especially in medical applications.

The inherent noise issue with many types of motors is the brushes.  Brushes create mechanical and electrical noise due to friction against the commutator, as well as arcing caused by current conducting through the brush and commutator.  A reduction in noise level of 10 decibels is an impressive achievement.  The decibel scale is logarithmic, not linear. Every three dB decrease of the sound level cuts the intensity of the sound by half.


Examine the following factors to reduced noise:

  • Look into different varnishing processes
  • Inquire about custom carbon brushes
  • Tighten machining tolerances

The data shown in the graph represents the 1/3 octave band testing data taken on a PMDC motor before and after the bullet pointed customizations.

For design engineers working on a noise reduction project, the motor design is only a part of the challenge. Radiated noise can be amplified through the other components in the system. Here are some additional tips for reducing noise:

  • Avoid using sheet metal and structural components that will resonate with the motor
  • In some cases, the use of vibration isolators to mount the motor can help
  • Accurately align of the driven components to the motor

*Note: the higher the RPM of the motor the more sound will be radiated from the motor.

Click on the link below for information on the Servo Motors available from Servo2Go.com –

Servo2Go’s Servo Motor Product Family

For more information, please contact:

Warren Osak
Toll Free Phone:   877-378-0240
Toll Free Fax:       877-378-0249


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