Noise floor (S/N ratio) test

JohnK · March 5, 2013

For everyone who is using the internal amp on their head unit, if you wouldn't mind running the following test I am curious to hear what you come up with.

I've attached a series of WAV files that each generate fifteen seconds of white noise at various low sound levels. I took a WAV file of white noise generated at 0db and dropped it successive amounts of volume. So "white-60db" means -60db, "white-80db" means -80db, etc.

The goal is to determine which of these audio clips you can hear above your radio's noise floor, and which ones you can't.

Copy all of the attached files onto a USB, SD.

Plug the card into your radio, open up the file with the highest sound level (e.g. white-60db), and put it on pause.

Flatten the EQ.

Raise the volume on your radio until you can hear a noise floor (hiss) coming from the speakers. On my stereo I can start hearing it in the 20-30 range.

Then repeatedly play and pause the audio clip, to see if you can hear the audio file material above the amp noise. If you hear the white noise on the audio clip, then your radio amp noise floor is below that level.

Progressively move to the lower volume audio clips, doing the play/pause toggle each time, until you find a clip that you cannot hear above the noise floor of your radio.

Please let us know which is the lowest level file you can hear. (For my test this morning I could barely hear -80db ... haven't checked -90db or -100db yet as I just made those)

Next, to hear the effect of the EQ, try bumping up the top 2 bands of the EQ by two notches each. For me this produced a noticable increase in noise floor of my radio. I imagine speaker differences will have an effect here as well.

You can also try this with a CD ... theoretically there should be no difference if the noise you hear is coming from the amp. It would also be interesting to hear how much better the pre-outs with an external amp do with this test.

Thanks. John