[smrtby123]

This is little note that I thought sci/eng nerds/majors like me might be into.

We were going over pressure measurements in my ME measurements class and the prof was defining dB's in terms of pressure. Calculating dB's follows this equation:

dB = 20log(10)(Pressure/2e-5 Pa)

Converting common dB's to Pascals/psi

60 dB = 0.02 Pa = 3e-6 psi (micropsi)

(Atmospheric pressure is 101kPa/14 psi, so it shows you just how sensitive your ears really are)

85 dB = 0.36 Pa = 5e-5 psi

100 dB = 2 Pa = 3e-4 psi

140 dB = 200 Pa = 0.03 psi

If you take the eardrum area to be about 0.55 cm^2 (0.09 in^2)
the force on your ear is only about 0.04 ounces but we're talking about a membrane that is most likely only a few micrometers thick (couldn't find any data online) so its quite a bit for it.

You can see how fast the pressure ramps up quickly, even a difference of 5 dB's makes a big difference on a log scale.


So watch your volume knob!!

 

[m0ofassa]

5 dBs is also a lot of volume, I might add.

 

[odigg]

The spending habits of Head-Fi members is very curious to me.

Thousands on headphone equipment and music, that's alright.

$50 USB on a SPL meter - that's way too much. I've actually seen threads where people seemed adamant about not buying an SPL meter and wanted a free way to figure out if their headphones were too loud.

Get an SPL meter! $50 is probably cheaper than a serious consult with your ENT specialist or audiologist.

 

[m0ofassa]

SPL meter is a waste of time IMO.

 

[MrKazador]

I can see why people don't want to spend ~$50 on something they'll only use once or twice.

 

[oca]

does a doubling in sound pressure level directly equal a doubling in loudness?

 

[m0ofassa]

its a logarithmic scale to my knowledge

 

[Buckster]

how exactly do you use a SPL meter to measure headphone volume

PX100 Sennheisers in my case

best reading I could get was putting the SPL meter head directly against the headphone cups and then cupping the rest to "seal"

 

[smrtby123]

Quote:

Originally Posted by oca /img/forum/go_quote.gif does a doubling in sound pressure level directly equal a doubling in loudness?

Its a semi-log scale so about every 6dB's you are doubling the sound pressure your ears are getting. The log scale is why it ramps up so fast.

60dB = 0.02 Pa
66dB = 0.04 Pa
72dB = 0.08 Pa

If you can get a good compact SPL I think it would be a good investment because you can benchmark all of your gear and make sure your levels are ok. You may think that you are in an ok range but come to find that you are creeping into the dangerous >85dB range.

 

[a3plew]

Since our ears aren't equally sensitive to all frequencies I think that the dba and dbc scales should be taken into consideration.(also exposure time) Basically the lower the frequency the higher the spl can be before it becomes unconfortable, painful, or damaging.

Just enjoy your music but don't overdo it. Occupational noise exposure. - 1910.95