pop when turning of light switch

So I did some lights on a 2009 nissan navara recently, a significant amount I might add, underbody, rotor, interior the whole nine yards, anyway, I wired them via a toggle switch and a relay, now my problem is, when the guy uses the switch and his audio is on when he turns off the light switch, he gets a pop through the mid range speakers, it was never there before, he has two amps, a 4000 watt class d exterminator and an 800 watt four channel for the mids and tweets, using a pioneer 500 ub head unit and a soundstream pre-amp. Any suggestions as to what might cause this, I didn't interfere with any wiring at the amps or anything to do with the audio, so I really don't know how the issue arose. Any possible solutions or suggestions as to what i can do to remove this would be appreciated, I have not done any trouble shooting yet,since he has'nt had time to return, but he will be back soon, just want a heads up as to what to look for. Thanks in advance.commit your way to jehovah and he will act in your behalf. psalms 37:5

https://www.the12volt.com/relays/page5.asp#ctm

Use the above link only to see how to position the diode across the coil of your relay. A diode is a polarized device.  It has to install across power and ground to the coil of the relay. 

That simple huh, I will try it and post back.commit your way to jehovah and he will act in your behalf. psalms 37:5

Yup, it really is THAT simple.

Hey IAAI, i have another problem with the same vehicle where the clock in the tachometer keeps getting thrown off everytime he switches the vehicle off and on again, any suggestions.commit your way to jehovah and he will act in your behalf. psalms 37:5

Define "Thrown Off". Does it reset to 12:00 or 1:00 everytime you power the key off? Or does it just lose the time that the key is off for?

If it's a reset as Sir Idiot Esq. is asking, that clock should have its own constant power feed as opposed to the switched power (IGN) for the tacho.

Did you get the popping noise to quit?