Decibel Readings

[RET_COP]

I was interested in decibel readings and could not find a lot of information in the cobra forums. I was able to borrow a decibel meter from my department and took some readings that I will post just for some information for all of us. You may draw some close conclusions from them or just have an idea what I am hearing.

I have a 24” scalloped baffle 2 ½ ID muffler inserts maybe slightly bigger but I did not measure it. I am not sure of the condition of the sound absorbing material behind the baffles except that they have 4000 miles on them.

I have a 357ci Windsor, 10.5:1 compression. Cam comparable to a CompCam XE294H, cleaned up windsor sr. roush 200 heads.

I took an industry standard reading at .5m or about 20” away from the tip of the exhaust on the same plane at a 45 degree angle, (A) setting on asphalt.

idle 95dB
3000rpm 110dB
At 10ft away idle same plane and angle 85dB
At 20ft away idle same plane and idle 80dB

Inside the car with HardTop 90dB cruising 2200rpm, to 100dB + driving hard.
Top off was not recorded but the noise at idle is lower.

Friends cars
406sbc 13.5:1 750HP with mufflers (see through perforated). At idle 100dB, at 3000rpm 118dB

510 bbc blown pro street about 700HP, spin tech mufflers. 100dB idle, 115dB 3000rpms

So there it is, I hope this helps a little.

Lou