how long is this wave?

[kreider204]

OK, we've all heard the myth that you have to be far away from a bass amp to hear the low frequencies because the bass frequency waves are supposedly so long ...

So, my question for you physicists / mathematicians: exactly how long (I mean literal physical distance) is the wave (one complete cycle) of the lowest E on a 4-string bass?

I'm guessing that we're talking tiny fractions of an inch, yes? Not several feet, as those who perpetuate that myth seem to suggest?

(Please keep your answers simple - I got a D in physics. )

[mikezimmerman]

A 41 Hz sound wave has a wavelength of about 27 feet in air at 20 degrees C, according to this calculator: http://www.1728.com/freqwavf.htm

There's also a chart here: http://www.phy.mtu.edu/~suits/notefreqs.html

Mike

[jelwood]

As a physics major at Cal Poly, Mike's answer seems to be in the right range.

[bongomania]

Originally Posted by kreider204

I'm guessing that we're talking tiny fractions of an inch, yes? Not several feet, as those who perpetuate that myth seem to suggest?

It's not that the waves are shorter than suggested--it's that we don't need to hear a complete wave cycle, to hear the sound.

[SactoBass]

Originally Posted by bongomania

It's not that the waves are shorter than suggested--it's that we don't need to hear a complete wave cycle, to hear the sound.

If we did, we would need to wear some mighty ridiculous looking headphones!

[PhiDeck]

The distance from your ear to a woofer's cone is irrelevant to being able to discriminate the frequency of the note being reproduced.

However, the duration of the note is relevant. Your inner ear is a spectrum analyzer. In order to differentiate one frequency from another, the sound must be present for a minimum amount of time. That minimum amount of time is inversely proportional to its frequency (or directly proportional to its wavelength).

[kreider204]

Originally Posted by bongomania

It's not that the waves are shorter than suggested--it's that we don't need to hear a complete wave cycle, to hear the sound.

AH! I gotcha, that makes sense.

Thanks everyone!

(BTW, I mostly got that D from skipping class a lot - honest. )

[Downunderwonder]

I know the distance is irrelevant but the duration? Really, or do we have another myth here?

What's a staccato 64th note worth, I'm picking less than 1/41th of a second?

[Rockmusician]

Looks like Mike got it right. I have always heard that it was between 25 and 30 feet.

[Hoover]

Originally Posted by Downunderwonder

What's a staccato 64th note worth, I'm picking less than 1/41th of a second?

If you could show me an example of a bass player executing a staccato 64th note on a low E (at any tempo brisker than the most lethargic ballad) I'd be able to point out how you're not actually hearing the fundamental frequency...but I'm pretty sure there aren't any examples of the former!

[mikezimmerman]

Originally Posted by Downunderwonder

I know the distance is irrelevant but the duration? Really, or do we have another myth here?

What's a staccato 64th note worth, I'm picking less than 1/41th of a second?

The duration is indeed important, because you have to hear at least enough of the waveform to be able to determine the frequency--how else would you know what it is? That's why MIDI conversion on bass has so much lag time in the lower registers.

Fortunately, since your brain is not doing MIDI conversion, it's not really necessary for you to be 100% sure what the frequency of a staccato 64th note is in order for it to have the desired effect musically!

Mike

[mikezimmerman]

Originally Posted by Hoover

If you could show me an example of a bass player executing a staccato 64th note on a low E (at any tempo brisker than the most lethargic ballad) I'd be able to point out how you're not actually hearing the fundamental frequency...but I'm pretty sure there aren't any examples of the former!

Oops, good point. The nice thing about bass (and most other instruments) is that the notes include a lot of higher-frequency overtones, so you don't need to hear the fundamental frequency in order to determine what the note is. If you were playing a 41 Hz sine wave, it would be a different story...

[251]

Originally Posted by mikezimmerman

A 41 Hz sound wave has a wavelength of about 27 feet in air at 20 degrees C, according to this calculator: http://www.1728.com/freqwavf.htm

There's also a chart here: http://www.phy.mtu.edu/~suits/notefreqs.html

Mike

<Edit 12/3/10>
Ignore what I have written below. It is incorrect & not very useful. OTH, it is an amusing example of how to embarrass yourself with a keyboard as you will see if you read down the sub-thread. 8-)


+1. full wave, 41Hz = 27 feet. That means standing out in the open (no reflecting surfaces) 13.5 feet from the speaker there is a minimum of sound & standing 6.25' or 19.75' from the speaker there are sound maxima.

Play with a 10 foot cord that touches the floor & you should be near the 6' mark & hear close to the maximum output. If you are dealing with a large room, a stage, a PA etc, you have to trust the sound engineer or a friend in the audience to help you match volume levels in a mix. You will never hear exactly what the audience hears in the center of a room. If you are on a small stage, close to your amp, you are likely to turn the volume up too high to sound good in the room. Sometimes, the best you can hope for is being able to hear what you are playing + the rest of the music.

[greenboy]

Originally Posted by 251

+1. full wave, 41Hz = 27 feet. That means standing out in the open (no reflecting surfaces) 13.5 feet from the speaker there is a minimum of sound & standing 6.25' or 19.75' from the speaker there are sound maxima.

Well, that's just as wrong as can be. Pity you worked so hard to supply some numbers.

Time to subscribe to a good trade rag if there is still one about, or read some pro audio sites or buy a sound reinforcement handbook.

The reason sound has been discussed as waves is because WAVES move. If nothing else, it's a good visualization tool to think of ripples in a pond when you drop a stone in. The wavefront is not stationary at some fixed measurement. The peaks and troughs move outward until they meet obstacles*. There you begin to come in contact with the idea of destructive cancellations and so forth.

Plenty of applet-based illustrations on the net on how this actually all works in a room.



*or have dissipated all energy in the medium, more often than not according to the inverse square law

[251]

Originally Posted by greenboy

Well, that's just as wrong as can be. Pity you worked so hard to supply some numbers.

Time to subscribe to a good trade rag if there is still one about, or read some pro audio sites or buy a sound reinforcement handbook.

The reason sound has been discussed as waves is because WAVES move. If nothing else, it's a good visualization tool to think of ripples in a pond when you drop a stone in. The wavefront is not stationary at some fixed measurement. The peaks and troughs move outward until they meet obstacles*. There you begin to come in contact with the idea of destructive cancellations and so forth.

Plenty of applet-based illustrations on the net on how this actually all works in a room.



*or have dissipated all energy in the medium, more often than not according to the inverse square law

I was taught in Physics, that sound is transmitted through air & water as standing waves. The air does not move across the room. The air in the room vibrates in place. It takes a lot more energy to move anything through the air at the speed of sound than my amp uses to get the job done.

That aside, moving air or not, the full wave (Sine) is 27 feet. There is a node (minimum amplitude) at the mid-point at 13.5 feet. There are anti-nodes (maximum amplitude) at 6.25 & 19.75 feet. That's Trigonometry, which is also used in Physics. It gets complicated when many standing waves are transmitted & that is what is described in the very useful manuals you reference.

[greenboy]

First, as I said, sound gets discussed as waves as a useful construct. It's a way to help visualize. Second, stationary nodes don't mean diddly until you actually look at the environment, or in the case of the musician, the venue.

[bongomania]

Originally Posted by 251

...moving air or not, the full wave (Sine) is 27 feet. There is a node (minimum amplitude) at the mid-point at 13.5 feet. There are anti-nodes (maximum amplitude) at 6.25 & 19.75 feet.

How wide do my headphones have to be, before I hear the bass notes?

[Jonathan1990]

http://www.phy.hk/wiki/englishhtm/Lwave.htm
See every horizontal line as a partical of air, then you'll get it.
Edit: click 'displacement vs t', just for the fun of it!

[251]

Originally Posted by greenboy

First, as I said, sound gets discussed as waves as a useful construct. It's a way to help visualize. Second, stationary nodes don't mean diddly until you actually look at the environment, or in the case of the musician, the venue.

We can agree about that.

[251]

Originally Posted by bongomania

How wide do my headphones have to be, before I hear the bass notes?

OT, apologies.
<edit>
Are we having a problem Cyrus? If so, let's take it to PM, please.