69
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
this post was submitted on 30 Nov 2023
69 points (94.8% liked)
Ask Science
8596 readers
1 users here now
Ask a science question, get a science answer.
Community Rules
Rule 1: Be respectful and inclusive.
Treat others with respect, and maintain a positive atmosphere.
Rule 2: No harassment, hate speech, bigotry, or trolling.
Avoid any form of harassment, hate speech, bigotry, or offensive behavior.
Rule 3: Engage in constructive discussions.
Contribute to meaningful and constructive discussions that enhance scientific understanding.
Rule 4: No AI-generated answers.
Strictly prohibit the use of AI-generated answers. Providing answers generated by AI systems is not allowed and may result in a ban.
Rule 5: Follow guidelines and moderators' instructions.
Adhere to community guidelines and comply with instructions given by moderators.
Rule 6: Use appropriate language and tone.
Communicate using suitable language and maintain a professional and respectful tone.
Rule 7: Report violations.
Report any violations of the community rules to the moderators for appropriate action.
Rule 8: Foster a continuous learning environment.
Encourage a continuous learning environment where members can share knowledge and engage in scientific discussions.
Rule 9: Source required for answers.
Provide credible sources for answers. Failure to include a source may result in the removal of the answer to ensure information reliability.
By adhering to these rules, we create a welcoming and informative environment where science-related questions receive accurate and credible answers. Thank you for your cooperation in making the Ask Science community a valuable resource for scientific knowledge.
We retain the discretion to modify the rules as we deem necessary.
founded 1 year ago
MODERATORS
There are two things making noise in the microwave when it's running. There's the transformer that's making the high voltage for the magnetron, which is you 120 Hz noise you're hearing.
The other noisy thing in the box is the fan. The fan is most likely a three blade metal fan running on a little shaded pole induction motor. That motor is very simple, just one moving part, and two poles. Two poles at 60 Hz gives us 3,600 RPM, which the motor can't quite reach because as the RPM gets closer to that magic number of 3,600 rpm, the motor draws lesa current and makes less power. This difference between the speed the motor is trying to run ("syncronous speed") and the actual speed is called the "slip" and is probably around 3%-5%. This gives us a fan speed between 3400 and 3500 rpm.
I don't know if that is giving you the second noise you're hearing, or if it's mixing with the transformer noise to make it. But now you've caused a situation where I'm going to be caught holding a guitar tuner to my microwave.
He did the math!
Can I give a second upvote to just the last sentence?
Wow. This question is a good but very specific observation, and I did not expect an actual answer.
I don't know much about music or why some sounds are more pleasant than others... but I do know about electric motors.