? Because the square dance play songs is wireless transmission, so you can interfere with wireless transmission, like setting up a walkie-talkie antenna on the top floor, and when the audio is too loud, adjust the transmit power to a maximum of 5 watts, and then adjust to the high frequency band, and then call.
For DIY players or audio users, often plagued by AC sound, ask around in the group, there is always someone who suggests that he increase the filter capacitor capacity, I can say for sure that 99% of the AC sound and the filter capacitor capacity has nothing to do. Audio noise (current sound) sources of interference, can be divided into the external electromagnetic field radiation coupled to the interference and the machine PCB wiring and installation of unreasonable interference.
(1) External coupling to the interference. Most of this interference is caused by the signal line, because most of the equipment have chassis shielding, exposed as an antenna can only be the signal line. To determine the external coupling to the noise or internal noise is very simple. Just short-circuit the input (i.e., turn the volume potentiometer all the way off or short the input terminals with short wires) and if the noise is gone.
That's the external problem, if the noise is still there (the noise size does not change with the volume potentiometer or changes irregularly), that's the internal problem. When the signal line is not connected to the preamp but is suspended, if the shielding is not very good, it is easy to hear the noise coupled from the signal line, and this noise volume is proportional to the input impedance.
The higher the input impedance, the higher the noise voltage generated by the noise current, which is amplified, the louder the noise is heard. This is why home HiFi devices have 50kΩ or even 100kΩ input impedance, while professional devices prefer 10kΩ-20kΩ input impedance.
Professional equipment signal line is long, low input impedance is conducive to reduce the signal line to lead the noise and improve the signal-to-noise ratio. Therefore, the low-frequency analog signal line, the core thickness is not thick clouds, the most critical is the shielding layer must be dense and thick. This is a really good line.
(2) chassis, circuit board design unreasonable interference. This interference has nothing to do with the outside world, the input terminals shorted will still have noise output, this noise belongs to the broad category of low frequency.