audax

iTrader: (10)

What exactly is meant by "Sound Pressure Levels"?

engin_ear

iTrader: (1)

Sound is basically the periodic compression and de-compression (called rarefaction) of air. Your eardrums measure the changes in pressure of the air in the ear canal, and this mechanical energy is converted to an electrical signal that your brain perceives as sound. That's how we hear. Consequently, sound is measured as a pressure level. This is a level that is relative to the quietest sound that can be perceived. It is measured in dB (decibels) relative to that level. You can use a sound pressure level meter to measure the sound level in a room or space. So if I measure 85 dB SPL, the sound is 85 dB louder than the quietest perceivable sound, etc.

about 60 db SPL = conversational level
about 85 dB SPL = shouting
about 120 dB SPL = rock concert
about 130 dB SPL = threshold of pain
about 150 dB SPL = your stereo is too loud
(seriously though, anything above about 90 dB SPL can have hearing loss effects depending on the exposure time - allowable exposure time is inversely proportional to dB SPL)

audax

iTrader: (10)

So Darius was just referring to the drastic increase in dB levels after adding Xtreme. Got it.

I was mainly curious if he was referring to something else. I've covered the entire interiors of my past two cars with Xtreme (front to back, roof to floor... everywhere). Both times I noticed that my ears had a higher tendency to feel "plugged up" when driving around... even with the stereo off. Wasn't sure if it was my imagination or if it was related to the sound deadening.

TwentyTen

Yes Dynamat increasing the SPL in your car not only improves the sound quality but can potentially save you money on amplifiers. Engin_ear will have to chime in to clarify for me but I think 1 decibel is the measure of 10 bels. Meaning 2db measures 10 times louder 1db, requiring substantially more power from your amps. This is why 1,000 watts may only yield a 5-10db gain over a 500 watt amp.

Engin_Ear: Great explanation! Thanks! Can you clarify my vague knowledge of db power requirements?

engin_ear

iTrader: (1)

Thanks Darius. OK, 1 dB (decibel) is actually one tenth of a Bel, named after Alexander Graham Bell (i guess they couldn't spell, but they could do logarithms...). It is defined as 10 times the log of the power difference (ratio), or 20 times the log of the voltage difference (ratio). For every increase of 3dB, you need twice the amplifier power, and this applies to SPL as well. This is why it is SO difficult for SPL competitors that are hitting 150+ dBSPL to generate even more output level - the additional power requirements for every 3dB increase become HUGE. Anyway, doubling the output power does NOT double the perceived loudness. You actually need a 10 dB increase in power to perceive the sound as being twice as loud.
To clarify your numbers above, the 1000 watt amp will only yield a maximum 3dB increase in output power over the 500 watt one.. Actually, a power increase of 1dB is only about a 25% increase in power, and is nowhere near the 10dB increase that you need to have to perceive the sound as twice as loud.
Take care of your hearing - once you lose it, you can never get it back.

TwentyTen

Thanks again, I'm going to have memorize that because my numbers were WWAAYY off!!! .

//Darius

xirforever

What companies of sound deadning mats do you guys like best? I keep hearing dynamat. Has anyone ever used RAAMmat? Or anything else?

engin_ear

iTrader: (1)

Dynamat Extreme is good but not cheap, and it doesn't smell at all like regular Dynamat. Many have used RAAMmat and Brown Bread. RAAMmat is cheaper than Dynamat.
I've also used regular Dynamat (very heavy and smells like asphalt), not recommended, and CAE. The CAE stuff is pretty thin but it seems to be OK for lining the inside of door panels. I wouldn't use it on, say, a rear deck.
Try this:
https://www.clublexus.com/forums/sho...hlight=raammat

xirforever

Yeah i had heard great stuff about RAAMmat and i like their prices a lot better. Thanks for the link and response

TwentyTen

I have only used Dynamat Xtreme. Like Engin_Ear said, it doesn't smell at all but it's very heavy. My trunk lids almost slams on its on when I close it. The bulk pack feels like 30lbs. If it's boomy sound you're looking for, Dynamat won't get you much of an increase in sound OUTSIDE the car but it will increase the clarity and pressure INSIDE the car. In my situation, it "cleaned" up the sound and improved the overall quality.

//

vin 78

2 bulk kits, 3 door kits, and 1 can of dynamat spray=couldn't be happier.
(one door kit per front door, and one door kit for the rears)
all dynamat xtreme

TwentyTen

Hey Claus, welcome to ClubLexus. Yes, adding DynamatExtreme will significantly decrease outside noise and car/bass vibrations. I can't remember if I mentioned this before but if it the attention grabbing boom you want, the Dynamat lowers the amout of sound that actually makes it out of the car...at least in my situation. But I have two sealed enclosures vs a ported box.

35lbs of Dynamat Xtreme can be found on eBay for about $110.00 shipped. I removed the rear sub so the bass could flow into the cabin. In the IS, I would recomment removing the speakers in the rear deck, depending on what kind of box you get. My trunk is kinda heavy. About 20lbs of Dynamat, 2 amps, 2 Subs in 2 sealed plexi/MDF boxes, car cleaning supplies, portable battery jump starter/jumper cable thing (HEAVY), first aid kit, and some basic tools.

Good luck, hope that helps...

TwentyTen

No problem, keep me posted!

ILOVEGIRLS

iTrader: (3)

darius.
do you know of anyway i can decrease road noise?

engin_ear

iTrader: (1)

I do. Drive without your engine running. You won't look good, but it'll sound good.