jargon

Fri Nov 18, 2011 11:51 pm   

What's the difference between reverb, echo, and feedback?


--
Rich

Fri Nov 18, 2011 11:52 pm   

On Fri, 18 Nov 2011 13:51:37 -0800 (PST), RichD
<r_delaney2001_at_yahoo.com> wrote:


http://en.wikipedia.org/wiki/Reverberation

Reverberation is the persistence of sound in a particular space after
the original sound is removed.[1] A reverberation, or reverb, is
created when a sound is produced in an enclosed space causing a large
number of echoes to build up and then slowly decay as the sound is
absorbed by the walls and air.


http://en.wiktionary.org/wiki/echo#Noun

A reflected sound that is heard again by its initial observer.


http://www.thefreedictionary.com/feedback

Sound created when a transducer such as a microphone or electric
guitar picks up sound from a speaker connected to an amplifier and
regenerates it back through the amplifier.
--
JF

Fri Nov 18, 2011 11:57 pm   

"Rich Dope"




** Depends on the context.

Digital delays and tape echo machines have controls with these names.



.... Phil

Sat Nov 19, 2011 12:08 am   

John Fields wrote:

Or, in an electrical circuit, when the voltage or current at a point in
the circuit is "fed back" to a point earlier in the circuit. Depending
on its phase, this can be either negative or positive feedback.

--
Virg Wall

Sat Nov 19, 2011 12:27 am   

On Fri, 18 Nov 2011 13:51:37 -0800 (PST), RichD <r_delaney2001_at_yahoo.com>
wrote:


Delay

Sat Nov 19, 2011 2:56 am   

On Nov 18, "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz> wrote:

Aren't they all delay?

--
Rich

Sat Nov 19, 2011 6:12 am   

On Fri, 18 Nov 2011 16:56:56 -0800 (PST), RichD <r_delaney2001_at_yahoo.com>
wrote:


Different delay (and decay). If the delay is on the order of a wavelength and
shorter than the decay, it's feedback. Greater than that it's reverb until
you can distinguish the individual images. Then it's echo. ...at least
that's how I see it.

Sat Nov 19, 2011 9:48 am   

On Fri, 18 Nov 2011 13:51:37 -0800 (PST), RichD
<r_delaney2001_at_yahoo.com> wrote:


Echo is a single reflection of a sound - the kind you hear when you
shout "Hello" near a cliff.

If you put together many echoes, arriving from different distances
into a jumble that you can't distinguish - that is reverb. You get
that in, say, a large church.

Feedback is a situation you only get when you have an amplifier and a
speaker. The sound arriving from the speaker is a little louder than
the one that originally hit the microphone, so that comes out of the
speaker a little louder still. This loop will build until the system
howls. You cure it by turning down the amplifier so the sound from the
speaker is always a little softer than the original when it hits the
microphone.

d

Sat Nov 19, 2011 10:22 am   

"Don Pearce" <spam_at_spam.com> wrote in message
news:4ec76c21.174471_at_news.eternal-september.org...

Multiple reflections are also common in such instances.



That would be *acoustic feedback* only, There are MANY other types of
course.



Or any other method that reduces the loop gain at the feedback frequency,
notch filtering being a common example.

Trevor.

Sat Nov 19, 2011 11:16 am   

On Sat, 19 Nov 2011 20:22:43 +1100, "Trevor" <trevor_at_home.net> wrote:


No they are not. One cliff, one echo. No choice.


- or even mention - other kinds.

Again, given the question, no need to complicate the answer.

d

Sat Nov 19, 2011 1:11 pm   

On Nov 19, 12:12 am, "k...@att.bizzzzzzzzzzzz"
<k...@att.bizzzzzzzzzzzz> wrote:

Perhaps we might ask the original poster what
is meant by "reverb" and "echo" and "feedback."

By "echo" and "reverb," do you mean the acoustical
phenomenon of echo and reverberation? Or do you mean
the analog or digital effects (simulations, if you
will) often labelled "echo" and "reverb"?

"Feedback" is, in some ways, an effect that's in a
different class. But all systems with a connection
between the output and the input are capable of having
feedback, By "feedback," are you talking about when
a system, breaks into self-oscillation, which means
positiive, regenerative feedback?



Wrong. Feedback requires two conditions: first, the delay
must be an integral multiple of a wavelength (or complete
phase rotations: essentially equivalent) and second, the
system must have a power gain equal to or greater than one.
Feedback cannot occur unless both conditions are present.
The requirement of gain in the system is what makes feedback
very different than either echo or reverb.

The notion that feedback requires a delay on the order of
a wavelength is easily shown to be false when one observes
acoustical feedback in amplified PA systems happening at
middle frequencies (several hundred to several thousand
Hertz) where the amplifier and speaker are quite some
distance apart, many dozens of feet, where the corresponding
delay between the two corresponds to many wavelengths.

In such a situation, one very quick cure is to turn the
volume down: this reduces the overall gain of the system
to less than 1, and the regnerative feedback then stops.
There's still feedback, but without the necessary gain,
the system no longer oscillates.


So, is there some specific delay value in which you claim
that an echo becomes reverb?

--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+

Sat Nov 19, 2011 5:40 pm   

The original post sounded like a homework question.

Sat Nov 19, 2011 6:19 pm   

On 19 Nov 2011 16:40:38 GMT, sgordon_at_changethisparttohardbat.com
wrote:


I'm not so sure. The feedback part was too far out of kilter with the
rest for any real physics teacher to have set it.

d

Sat Nov 19, 2011 6:26 pm   

I was thinking of a recording class in a music department.

In rec.audio.tech Don Pearce <spam_at_spam.com> wrote:
: On 19 Nov 2011 16:40:38 GMT, sgordon_at_changethisparttohardbat.com
: wrote:
: >The original post sounded like a homework question.
: I'm not so sure. The feedback part was too far out of kilter with the
: rest for any real physics teacher to have set it.
: d

Sat Nov 19, 2011 6:38 pm   

On 19 Nov 2011 17:26:59 GMT, sgordon_at_changethisparttohardbat.com
wrote:


Ah. That probably makes it worse, not better.

d