Author Topic: Where is electronic noise cancellation technology?  (Read 6784 times)


  • Guest
Where is electronic noise cancellation technology?
« on: December 19, 2006, 05:23:09 PM »
I'm wondering what's up with that. For instance, I have a noisy hot tub. It seems to me that a simple solution would be to install a noise cancelling device inside. In principle, it's a microphone and a loudspeaker. The microphone records the sound, a computer chip reads and converts it into the same sound but phase reversed so that the sound waves cancel each other out, and shoves that 'negative' sound back out to the speaker. This works best where the sound does not vary much - as in this case.
This technology has been in use eg at hyrdopower plants in the engine room where huge turbines make unbearable noise. And that was 30 ys ago.
Nowadays you can get noise cancellation headphones for $50. What gives? I'm tempted to buy a set and experiment.


  • Guest
Re: Where is electronic noise cancellation technology?
« Reply #1 on: December 19, 2006, 05:55:47 PM »
We get lots of requests for info about noise-canceling, or Active Noise Reduction.  (ANR)  In Desert Storm, the enemy were astounded and dismayed when they couldn't hear  the American tanks drive right up into their camps!  Here's a link to a site on that subject.
Some of our customers have had good results by "Masking" annoying, intolerable noise with white noise generators made by MARPAC  or SCAMPMASK .  To see if this will work for you, use a FM receiver tuned to between stations to see if this will tend to mask your noise source. A running fan will sometimes work, too.  We also have regular headsets (earmuffs) .



  • Guest
Re: Where is electronic noise cancellation technology?
« Reply #2 on: December 19, 2006, 11:09:55 PM »
Electronic noise cancellation has been oversold and overhyped.  It works fairly well in some cases (headphones, machinery making 'pure' tones) but in the real world, with so many factors and variables, it is almost worthless. 

If you want to quiet your hot tub, start with the motor.  Most of the noise is coming from the vibration the motor is transfering to the frame/structure.  Mount the motor resiliently, with rubber pads.   Then focus on reducing the airborne noise coming from the motor & pipes.  Add more mass to the enclosure, make sure any doors/hatches shut and seal up nicely.  Insulate the underside of the tub if possible (if not already done.) 

(All true above: In addition, cut the a section out of the in/out piping connecting the pump.  About 2" is good.  Then use a radiator hose from the local auto supply co to re-make the connection.  This isolates the vibration coming from the motor/pump into the rigid pipes of the hot tub.  Thiese pipe radiate noise like piano strings if left connected to the pump!  BJ Nash).