And so I have started to build my version of the poor person's ``noise-cancelling'' headphones. Basically, I got a decent A-weighted ear protection device in the form of ear muffs (for about 20 dollars), and stuck them on top of my in-ear headphones, whatever they maybe. Voilà, noise-cancellation system without the associated 300-dollar price-tag. The good thing about this is that if I'm sick of hearing the noise that surrounds me, I can substitute my earplugs for my headphones, which attentuates most of the sound. Check out the frequency response rate of both:
| Freq. (Hz) | 125 | 250 | 500 | 1000 | 2000 | 3150 | 4000 | 6300 | 8000 |
|---|
| Muffs | 20.7±2.5 | 25.2±1.9 | 36.2±2.5 | 43.4±2.4 | 36.0±2.0 | 35.3±1.9 | 37.3±2.0 | 36.0±1.5 | 36.3±2.2 |
| Plugs | 38.4±2.9 | 40.3±3.5 | 43.2±4.0 | 41.8±3.8 | 38.6±2.6 | 45.0±2.8 | 45.7±3.5 | 49.6±3.8 | 47.3±4.3 |
Where the number given is measured in dB (mean±standard deviation) with a reference level of 92dB(A) as the environmental noise. I will not attempt to calculate what the effect is from using both at the same time---I can't tell the covariance between these two sets of data and thus cannot estimate the correct quantities needed. Suffice to say, if I put on both at the same time, someone has to yell rather loudly for me to be able to hear him/her.
Alright, enough of mumbo-jumbo, I need to get to class for my midterm (again). Sigh.
[Ed: If the numbers in the table seem too small, blame IE for rendering things without regard to actual size and dimensions---I had to hack the table to make it fit that way]
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