Topic: Frequency range ?

[John Kelly]

you know if you play a 21Hz tone loud enough and with enough power it will loosen your sphinctor muscle and you'll have to immediately crap.

"You guys!  You guys!  I found the brown noise!"
/south park

[Chuck]

Like any technical specification, quoted frequency response has to have a quantifier:
ex. 20Hz - 20kHz +/- 2db
In this example the frequency response can wander up and down a total of 4 db.
So typically the response will be 2db down at the extremes of the frequency range on that microphone.

A spec: 20Hz to 20kHz is useless information unless the quantifier is included.

[BobW]

Wouldn't that be 60 Hz (with 120 as the first harmonic)? AC power oscillates at 60 Hz, at least in the US.
-Matt

120 Hz is the sound of a loose ground at the speaker connection or on an analog RCA input.

No, it's 120Hz.
The 60 HZ is doubled by the rectifier (heh-heh, he said rectifier...) in the power supply.
Even more confusing is the fact that we're used to hearing the 240Hz first harmonic through small speakers, which act like an HPF
and cut off the 120Hz...........

Great reminder on the A/C rumble. It is that season again.

+T to the thread ! 1000 posts !

[markgarrigan]

So what would this spec mean?

12dB per octave at 100 Hz

[nic]

So what would this spec mean?

12dB per octave at 100 Hz

I'm assuming this is for a HPF(bass rolloff). starting at 100Hz, the signal is attenuated 12db(steep curve) going down to 0Hz.
if for a LPF(high end rolloff), then it would attenuate the signal by the same curve but for frequencies above 100Hz, only allowing frequencies below 100Hz to pass

an electronics major can give you a more detailed explanation

[F.O.Bean]

pretty much nailed it on the head there bro, it attenuates all freq below/above a certain frequency

attenuates basically means 'kills'

[markgarrigan]

sorry...i guess i didn't post the whole spec...

Switchable Hi-pass Filter, 12dB per octave at 100 Hz

So is this as luvean said a LPF(high end rolloff)?

if it "kills" all freq above 100 Hz isn't that a bad thing.  Wouldn't you only get low end then.  since the range goes all the way to Khz.  Why would you turn this on?  Or is the key phrase "per octave"?  In whitch case i would need further explanation.

[nic]

"Switchable Hi-pass Filter, 12dB per octave at 100 Hz"

this means that signals below 100Hz are attenuated

[MattD]

To add to luvean's post, this means that at 50 Hz, the signal is 12 dB lower than it would have been without the filter and at 25 Hz, the signal is 24 dB lower than it would have been.

[nic]

To add to luvean's post, this means that at 50 Hz, the signal is 12 dB lower than it would have been without the filter and at 25 Hz, the signal is 24 dB lower than it would have been.

so in this case, 50Hz is 1 octave lower than 100Hz?
Iv'e never quite understood the whole "octave" part...

if the HPF was at 200Hz, would the first octave be at 100Hz?
guess what I'm asking is, what frequency(range) is considered an octave?

[MattD]

Any doubling/halving of frequency constitutes an octave. This is pretty easy to understand if you draw it. Draw a sine wave, then draw another one at 2x the frequency of that one. In this example, you'd fit 2 complete cycles of the higher frequency wave in one cycle of the lower frequency wave. The resulting notes are the same, one octave apart.

Octaves have no set range of frequencies. In lower notes, the difference between 40 and 80 Hz is an octave, but with higher notes, the difference between 1000 and 2000 Hz is an octave.

You're right with your HPF example there.

[Sean Gallemore]

high pass filter means the lows are cut, which means the highs pass through without being affected.

If the HPF is 100hz @ 12dB/oct. then the roll-off starts at 100 and theoretically at 50 hz (one octave down from 100) the signal should be 12 db lower and at 25hz (2 octaves down) the signal should be at 24dB.  The rating is just an estimate though because the actually roll-off is a curved slope, or maybe it's not and it just appears that way on paper