Wikipedia
Mains hum
Mains hum, electric hum, or power line hum is a sound associated with alternating current at the frequency of the mains electricity. The fundamental frequency of this sound is usually 50 Hz or 60 Hz, depending on the local power-line frequency.
https://en.wikipedia.org/wiki/Mains_hum


BK-9 BACKING KYBOARD
- Ako uređaj koristite u blizini pojačala ili druge opreme sa jakim transformatorima može se pojaviti brum. Da uklonite taj problem, promenite položaj ili orijentaciju uređaja, ili ga udaljite od izvora smetnji.
http://www.rolandplanet.rs/uputstva/BK-9-Uputstvo.pdf
- Using the unit near power amplifiers (or other equipment containing large power transformers) may induce hum. To alleviate the problem, change the orientation of this unit; or move it farther away from the source of interference.
https://static.roland.com/assets/media/pdf/BK-9_e3.pdf


S. B. Tankosić, Politehnički rečnik
hum - šum, fon naizmenične struje, brujanje