Active speakers picking up cellular tower waves? Since a week or so a constant high pitch sound (~4khz) emanates from my active monitor speakers. After eliminating any ground or power source issues I noticed, that the sound rises in volume whenever I open my window - which is exactly between my speakers and an array of cellular antennas on the opposite building. I recall there were new antennas added a few weeks ago. Our public database shows that there are over 20 transmitters on there, with 3 pointing exactly in my direction.
Question: Can HF-EMWs produce such a sound in an audio amplifier or through it's connectors (it's not the cables or whatever comes through them)?
 A: Most certainly Radio waves can be picked up by other, unintended devices. There are strict rules governing interference,( FCC ) you might want to contact them. 
But, you can also try to block the waves, If you know the frequency, then a wire mesh at half the spacing of the wave placed around the device being interfered with should stop the unwanted effects. The cage does not have to be grounded. If frequency is unknown, then a solid metal barrier should stop the signal. 
But, Of course you will want to use the device, so, placing two diodes in line just before the speakers should be able to arrest the situation. You will want them small enough ( micro ferret range ) to allow a normal signal to pass through them but large enough to stop the interference. the Diodes should be placed on the positive side, with the direction of flow in opposite directions.( One running positive to negative, the other negative to positive) on only one wire. TO be clear, you are placing both diodes on one wire, breaking the wire, and adding a connection to both diodes that are place in opposing directions of flow, then the line will continue to the terminal of the speaker. Hope that is clear. 
The diodes will block any signal that does not have enough strength to overcome the Diodes' potential. Since the interference is an induced field, it's strength should be relatively low. When a signal is sent from the system to the speakers, the strength should be great enough to pass over the diode bridge without any obvious loss of volume or clarity. Good luck. 
A: Considering that cell phone towers broadcast at frequencies that start at ~ $100$ $MHz$ and go on all the way up to nearly $1$ $GHz$, I'd say that the interference you're hearing isn't due to the cell phone towers.
But to answer your other question - It is possible for electromagnetic radiation to induce a signal in an audio amplifier. An amplifier takes an electrical signal, sends it through some circuitry to boost the amplitude, which then drives a speaker of some manner. 
An electromagnetic wave will induce oscillations in the amplifier circuit (exactly the same way as an antenna), which will presumably be amplified and that's the hum that you hear. 
I doubt that it's the cell phone tower, because it will induce a frequency comparable to it's transmission frequency, and if you are hearing something at ~$4$ $KHz$, then it's way too low a frequency to be caused by the cell phone signal. 
A: I can now safely say that it's LTE. For anyone interested: There are all sorts of lower frequency carrier waves that are then modulated with the actual HF. For UMTS, LTE or Bluetooth, perfectly distinctive sound signatures can be made audible with measurement-tools. Or a pair of KRK speakers that is, even with magnetic shielding. Although readings indicate a really unhealthy dose of radiation (6 μW/m2) in my room, it is still far below any judicial threshold.
A: Same issue Here, I have a 4G tower 100m away in front of my windows and picking High pitched noise at frequencies of 4kHz, 6kHz and 8kHz. The noise appeared when the 3G cell towers were replaced by 4G towers.
The best solution I found was to wrap the active speakers in an emergency blanket (all the faces except the one containing the speaker). This drastically reduced the noise.
