Question

I would like to know how can I calculate loudness using steven's law ?

I have a range of decibels on hand and I know steven's law has one equation loudness = k * intensity^0.67 for sound. But when I sub in the values of decibels into the equation, all I'm doing is changing the scale of the axis and my lecturer suggested reading on equal loudness contours mentioning steven's law is not straight forward. So how exactly can I calculate it. Supposingly I have 50 values of decibels from 50 - 100 db.

Answer 1

hi. This is good old acoustics, by the sound of it, so to speak. So, you're trying to think in terms of bels and decibels on a LOGARITHMIC scale. Log to the base 10, as i vaguely remember it. If there's an INTENSITY involved then I think it 10 log10 of the value. If there's an AMPLITUDE then I think it's 10 log10 of the value. It MAY be that the 0.67 index fits in here somewhere here. Regrettably, this is mostly memory guesswork. dB is a unit which is everywhere in science/technology, and I'm scratching my head.
bon chance et bon voyage
http://perendis.webs.com

Answer 2

There could also be "sones" and phons tied up here. And, there's maybe that there's effectively two parts to acoustics (as there is with radioactivity). One part is the, basically, LONGITUDINAL vibration of the COMPRESSION waves that are sound waves as they go through the required medium (ie not in vacuo). Then, there's the way that they are "perceived" by the recipient so to speak. So, a vvvv loud aircraft might produce a noise level in the 120dB area - nearing the threshold of pain to a "normal" listener but, presumably NOT to someone who is DEAF. The UK "musician" Pete Townshend has gone deaf from playing all the stuff he plays/played.
Sorry about the waffle.

Answer 3

I'm thinking using the range of the decibels i have to perform a fft and retrieve the frequency then using the equal loudness contours to find the estimated phon then sones. But my fft contains large number of spikes, is there a way to reduce the impact of "unimportant" spikes ?

Answer 4

Wow. you do go for the jugular with the questions. The fft = fast fourier transform, I take it. Yes, I think that there is a way of reducing, as you say. It's called a FILTER. There's something in optics which I painfully seem to remember is called APODISATION. Basically in OPTICS you get the FT fourier thing of the object. Then, you stick a screen with with holes in it such that the FT orders that you want can pass through the screen, and the ones you want to filter get, .... well filtered. BUT, of course, optics is visual (never !) and it's sort of three d as well.
It MAY be that you need a lot of values to form a decent sized sample for your fft, bearing in mind that STATISTICS plays, I think, some role in this.
I regret being vague, but maybe we both wonder if I know what I'm talking about. Just before my head explodes ...
bon voyage, and keep me informed. It sounds a dam' sight more interesting than posts about projectiles and other bits of mechanics.

Answer 5

I get the impression (I guess) that this post is about undergraduate/postgraduate physics ? I've not bet on it, but I'd put 0.01 GBP on it ? Do I win 1p UK money ?

Answer 6

nah mate, the pound ain't worth pellet anymore!! you might get a few drachma or lira, if you're very lucky

:-))

Answer 7

ok, so do I win a pellet ? I guess you're referring to the "UK" referendum vote result and aftermath ?

Answer 8

BREXIT

Answer 9

The enclosed might give an FFT some wobblies, and it might hint at sound intensities and frequencies. I think that the singer is Diva Maria Callas, the song is "un bel di vedremo) (one fine day we shall see), and the TRAGIC opera is "Madama Butterfly".

Answer 10

In those days they had rules.

Amy Winehouse had no rules!!