Ouch--what the hell is that noise??

[usinjin]

So today, I started my ZHP and put it in reverse to head home. When I started backing up, I encountered a strange phenomenon that I'm not even sure how to explain properly. From a stop, my car made this dreadful "thud" sound--while it was stopped it did not make the noise, but as I reversed, it increased in frequency-- *thud.....thud.....thud..thud..thud thud thudthudthdthdddd d d d ddddddddd*. The sound, as best as I can describe, was the same dull thud of bass-heavy music you might hear from a car stopped next to you at a light. It also seemed to be coming from my subs. It was a very low-frequency (pitched) note--probably less than 100hz. It literally sounded like a pure "tone", NOT a mechanical thump at all. It was quite loud, in the sense that I more "felt" it than heard it. It did the same thing driving forward. I stopped with the car running and gave it a look over, underneath and in the trunk. Nothing seemed out of the ordinary. The radio was not on (it rarely is in my car). When I drove off again, it no longer made the sound..or so I thought. As I came to a stop again I could hear the same "note", but very quietly. Am I crazy? Is it coming from something else?

[fredo]

Mmhh ... how old is your battery ? I hear strange stuff happens with old ones. In this case, the sound system may be affected. :dunno

[ComradeNick]

So today, I started my ZHP and put it in reverse to head home. When I started backing up, I encountered a strange phenomenon that I'm not even sure how to explain properly. From a stop, my car made this dreadful "thud" sound--while it was stopped it did not make the noise, but as I reversed, it increased in frequency-- *thud.....thud.....thud..thud..thud thud thudthudthdthdddd d d d ddddddddd*. The sound, as best as I can describe, was the same dull thud of bass-heavy music you might hear from a car stopped next to you at a light. It also seemed to be coming from my subs. It was a very low-frequency (pitched) note--probably less than 100hz. It literally sounded like a pure "tone", NOT a mechanical thump at all. It was quite loud, in the sense that I more "felt" it than heard it. It did the same thing driving forward. I stopped with the car running and gave it a look over, underneath and in the trunk. Nothing seemed out of the ordinary. The radio was not on (it rarely is in my car). When I drove off again, it no longer made the sound..or so I thought. As I came to a stop again I could hear the same "note", but very quietly. Am I crazy? Is it coming from something else?Could be the brakes, my car can feel like that if the rotors are really wet but it goes away after using them a bit and drying them off.

Sent from my SM-G973U using Tapatalk

[usinjin]

Mmhh ... how old is your battery ? I hear strange stuff happens with old ones. In this case, the sound system may be affected. :dunno

This seems plausible. The battery is several years old (replaced by last owner, so not exactly sure when), and is an AutoZone roadside assistance battery (according to the label on the side at least).


Could be the brakes, my car can feel like that if the rotors are really wet but it goes away after using them a bit and drying them off.

Sent from my SM-G973U using Tapatalk

Could be—though it wasn’t wet, plus I have newish rotors + pads. When your rotors were making noise, were you stepping on the brakes at all? Also, could you feel a shudder when hearing the noise? I felt nothing, which seemed mysterious.

[usinjin]

I managed to get an audio recording. This was stopped at a light and then acceleration to about 40 mph. My iPhone doesn't pick up the bass that well--the sound is REALLY deep and loud. Notice that it continues on at the end at the rate of about 1/sec..this was while I was stopped. My car has no mods whatsoever (save for the mechanical fan delete)

https://drive.google.com/file/d/0BzAIe8014AKtQXFnelEybTE3T1RYVjZMcUx4VEJoU05fZF8w/view?usp=sharing

[racer2086]

Does it follow the frequency of rotation of the wheels/driveshaft? I would be suspecting a wheel bearing or driveshaft CV joint or center bearing.

[usinjin]

Does it follow the frequency of rotation of the wheels/driveshaft? I would be suspecting a wheel bearing or driveshaft CV joint or center bearing.

It continues when the car is stopped, exactly 1 thud/second. It’s definitely coming from my subs—will replace the battery and report back!

[GotZHP]

It continues when the car is stopped, exactly 1 thud/second. It’s definitely coming from my subs—will replace the battery and report back!

Double check all of your wiring and connections too. I had weird issues with my sub when the grounding cable was a little loose. Def sounds like an electrical issue and it may subside while driving faster because the alternator is spinning? Just some thoughts