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Handling Ultrasonic Cleaner Noise

This post title would appear to be a contradiction in terms when considering the strict definition of ultrasonic or ultrasound – that is sound that cannot be heard or sound above the audible range. This is generally pegged at above 20 kHz.

Common ultrasonic frequencies generally range from 25 kHz used to clean heavily soiled welded, cast and fabricated parts to 130 kHz used for very fine cleaning of highly polished surfaces or fragile components.

In fact ultrasonic cleaners do create audible sound. What is heard is not the ultrasonic vibration of a cleaner’s ultrasonic transducers but instead from what OSHA calls subharmonics set up by the cleaning equipment including the tank, the tank enclosure, lids, and parts being cleaned. Subharmonics can be defined as sound waves with frequencies that are a fraction of the original ultrasound frequency and therefore may be audible.<

Cavitation – the implosion of minute bubbles that do the cleaning – produces an audible “hissing” sound as well although not as noticeable as those created by subharmonic vibrations.

Dealing with Ultrasonic Cleaner Noise

The noise levels created by ultrasonic cleaner operation is more pronounced at lower frequencies such as 25 kHz and drops off significantly at frequencies of 37 and 45 kHz and higher. Repeated exposure to subharmonic noise emanating from an ultrasonic cleaner can be, well, annoying and impact personnel productivity. There are a number of ways of dealing with ultrasonic cleaner noise. Here are three:

  1. Ear protection. These have the advantage of muting the subharmonic sound but in doing so also impede the ability of an employee to hear instructions. We won’t comment on employees who have their iTunes plugged into their ears. This is an HR issue.
  2. Equipment enclosures. An OSHA report notes that high?frequency noise is highly directional and is associated with short wavelengths, meaning that it is easily reflected or blocked by a barrier or absorbed by acoustic materials.
  3. Enclosures can include lids, some of which are provided with ultrasonic cleaners or ordered as an option. Insulated lids offer improved noise deadening. All lids have the advantage of reducing cleaning solution evaporation and the loss of heat when cleaning solutions specify elevated temperatures.

A 25/45 kHz Elma X-tra Basic with insulated lid.

Turning off the ultrasound when the cleaner is not being used is a good method of dealing with subharmonics and saving energy at the same time. The point we want to make is that ultrasonic “noise” should not be ignored. Contact our ultrasonic professionals at 973-440-2191 for suggestions on how you can make your cleaning operations as user friendly as possible.


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