| experience with monitoring that signal, there is always going to be some level of noise you would hear. The base voltage of the sensor is around 2.25 volts and any vibration in the engine is translated into a deviation of that baseline voltage. This image is from my original data acquisition setup I put in my Z - it shows a plot of the detonation sensor voltage output: This is at idle. You can see the pulses generated from each cylinder firing.
 This is at 6500RPM. You can see that there is now a variation of about 0.25v and there is so much engine vibration that the pulses aren't distinguishable. IF you think they are, within that 200ms sample you should be able to count about 65 discrete pulses. (6500/60/5*3)
The detonation sensor is not a discrete sensing device; it is not listening solely for detonation and putting out a signal only when detonation is detected. It is basically always spitting out noise who's nature is specific to the noise in the engine - increasing in volume and pitch as RPM and load increase. The interesting thing about it is that the ECU does not listen for detonation past about 3600RPM because there is so much noise in the engine at higher RPM that it cannot differentiate mechanical noise from detonation. It is interesting that you can hear it over all the other noise. I'm really thinking that the noise you are listening to with the headset on your ears is drowning out the rukkus that is actually coming from your engine - 24psi is high for pump fuel regardless of what kind of turbos you have.
Could you explain what you hear through the headphones? I'm interested to hear about it.
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Interesting thing there with the headset.. From my - 
