Static Noise in Audio during washing machine operation

[thatsashok]

I have a question that has been bugging me every weekend while washing clothes with music On and being a mechanical engineer my knowledge has been limited to analyse the problem (momentary discomfort) at hand and expecting that the electrical engineers in the forum will help me understand

I notice that when the washing machine is working there is static noise produced in the PC audio speakers & this noise occurs momentarily and exactly in sync with the time when the motor of the washing machine changes direction of rotation during the tumble wash.

Another observation I have is that the static noise (volume/sound intensity) does not increase or decrease with the change in the volume output of the 2.1 Audio system via Knob or increasing the PC volume.

My questions are

• Why should a noise be produced in my Audio speakers when its audio input (Aux, no DAC) via PC are appliances that work on DC ? I understand that both PC and Speakers draw power from same home AC circuit
• Is this phenomena normal ? the building I live in is Old (electrical wiring and safety features wise) if that help

I may be wrong in assuming some of the things, but would like to understand this phenomena in details technically and learn more about it

Looking eagerly for the responses

 

[whitestar_999]

Seems like electrical interference in power line. Psu in pc convert ac to dc but speaker runs on ac only. I am not an electrical engineer though,this is based on my own knowledge so may not be correct.

 

[patkim]

Note that I am not a subject matter expert but giving a general theory that I am aware of and some pointers for troubleshooting

Whenever motion of electrons is suddenly disturbed random electromagnetic field (RF Radio frequency) is created. This is a universal principle. Motors draw a large starting current whenever they start and then they stabilize the current utilization. This process is repeating every time motor starts in the washing machine looks like.

In electrical and electronics that involves AC current, whenever automatic switching is required it’s generally attempted at 0 Volt position of the sine wave when the current is zero to ensure that switching will not generate RF interference. This is a design feature.

Now somehow it seems that the RF is generated by motor operation & is being captured by the sound card circuitry or the multimedia speaker’s circuitry as a momentary noise interference. Every electronic circuit be it AC or DC could be susceptible to RF interference and it can give off interference too.

Troubleshooting pointers

1. Use friend’s speakers at the same AC outlet and same PC. If noise goes the current speaker’s circuitry was susceptible to the RF interference. If the noise remains may be the sound card circuit on the motherboard is susceptible or possible issue in the AC input line.
2. Use the same speakers with different input at the same AC outlet. Say give output of your mobile phone MP3 player using an Aux cable.
3. Shift the entire unit to a different AC outlet if possible
4. Shift the speakers with mobile phone input to a different AC outlet
5. Try such combinations to see if you can isolate the issue
6. Get the earthing checked by a qualified electrician
7. Is switching motor direction causing any momentary load on rest of the equipment e.g. does a tube light very slightly dim when it happens?

Edit--
Record the audio using Audacity if sound card supports Stereo Mix as recording device when washing machine is in operation and play the saved audio later, is the noise heard in the recording?

 

[bssunilreddy]

Seems like electrical interference in power line. Psu in pc convert ac to dc but speaker runs on ac only. I am not an electrical engineer though,this is based on my own knowledge so may not be correct.

Yes what you said is absolutely correct.

 

[Zangetsu]

This generally happens when there is disturbance/surge in electric current.. like I hear a cracking sound from my speakers when such instance happens.

 

[thatsashok]

This generally happens when there is disturbance/surge in electric current.. like I hear a cracking sound from my speakers when such instance happens.

Same problem actually I think

Seems like electrical interference in power line. Psu in pc convert ac to dc but speaker runs on ac only. I am not an electrical engineer though,this is based on my own knowledge so may not be correct.

Oh. I did not know that.

Also I posted the thread on other forum [TE] and most replies there point me in the direction of a faulty electrical grounding of electrical circuit of my flat. I am going to get this checked by Electrician.

@patkim Interesting. Will do all of that and contact you.