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Volume (decibel) Low-pass filter (NOT frequency filter)

K

KeeperOfLogic

Jan 1, 1970
0
Hello,
I need a circuit for building a volume low-pass filter. why?
The problem is that every time there is a commercial on TV they
increase the sound level. I want to combat this by building a maximum
sound cap limit (adujstable via Pot.). It should work on all frequency
and should not reduce sound for any db lower then the cap limit.
Now the best version of this is that the cap is automaticaly based upon
the avarage volume, so this will work in every sound levels (meaning
cap = normal sound+10db, for example).
But it this is too complicated then a fixed cap with pot. will be
enough.

Since I have only very basic knowledge of electronics, a reference to a
detailed site will be nice.
Thank!
 
B

Bob Masta

Jan 1, 1970
0
Hello,
I need a circuit for building a volume low-pass filter. why?
The problem is that every time there is a commercial on TV they
increase the sound level. I want to combat this by building a maximum
sound cap limit (adujstable via Pot.). It should work on all frequency
and should not reduce sound for any db lower then the cap limit.
Now the best version of this is that the cap is automaticaly based upon
the avarage volume, so this will work in every sound levels (meaning
cap = normal sound+10db, for example).
But it this is too complicated then a fixed cap with pot. will be
enough.

Since I have only very basic knowledge of electronics, a reference to a
detailed site will be nice.
Thank!

The device you need is called a limiter, which is a
special form of compressor. (The term 'limiter' is
used for lots of other circuits; this one is specific
to audio.) These are (or used to be, anyway)
standard devices around recording studios.
The basic idea is that the circuit monitors
the average volume and if that exceeds the preset
limit it starts applying gain reduction to keep it at
the limit.

There will be a tradeoff between speed of operation
and audible artifacts like distortion. You don't want
to have it react so fast that it clips individual peaks,
or you will have horrid distortion. But if you set it to
react too slowly, there will be overshoot and "pumping"
effects. A typical approach is to make the release
time longer than the attack time to help reduce the
pumping.

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
 
B

BobG

Jan 1, 1970
0
Bob said:
There will be a tradeoff between speed of operation
and audible artifacts like distortion. You don't want
to have it react so fast that it clips individual peaks,
or you will have horrid distortion. But if you set it to
react too slowly, there will be overshoot and "pumping"
effects. A typical approach is to make the release
time longer than the attack time to help reduce the
pumping.
===============================================
One brute force way of achieving this goal (probably suitable only for
rich TV watchers) is to hire a carbon based semi intelligent volume
control technician that adjusts the audio gain up and down during
commercials to match the boss's desired psychoacoustic reference level.
 
C

Chris

Jan 1, 1970
0
KeeperOfLogic said:
Hello,
I need a circuit for building a volume low-pass filter. why?
The problem is that every time there is a commercial on TV they
increase the sound level. I want to combat this by building a maximum
sound cap limit (adujstable via Pot.). It should work on all frequency
and should not reduce sound for any db lower then the cap limit.
Now the best version of this is that the cap is automaticaly based upon
the avarage volume, so this will work in every sound levels (meaning
cap = normal sound+10db, for example).
But it this is too complicated then a fixed cap with pot. will be
enough.

Since I have only very basic knowledge of electronics, a reference to a
detailed site will be nice.
Thank!

Some information to supplement Mr. Masta's answer can be found at
Wikipedia:

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

Unfortunately, a hardware solution isn't going to happen at the
hobbyist level -- limiters are complex and expensive pieces of
equipment (otherwise we'd all have them).

Cheers
Chris
 
C

Charles Schuler

Jan 1, 1970
0
KeeperOfLogic said:
Hello,
I need a circuit for building a volume low-pass filter. why?
The problem is that every time there is a commercial on TV they
increase the sound level. I want to combat this by building a maximum
sound cap limit (adujstable via Pot.). It should work on all frequency
and should not reduce sound for any db lower then the cap limit.
Now the best version of this is that the cap is automaticaly based upon
the avarage volume, so this will work in every sound levels (meaning
cap = normal sound+10db, for example).
But it this is too complicated then a fixed cap with pot. will be
enough.

Remote control with "mute" is the only practical answer.

You could build up a peak detector or an average detector or an rms detector
(each getting more involved, from left to right) and still find that falsing
and failure to trip problems would drive you nuts.
 
K

KeeperOfLogic

Jan 1, 1970
0
Thank you all for your comments. I thought that if freq. filters are so
easy to made, then volume shouldn't be a problem. But I see that there
is a consensus among you about the ineffectiveness of building one. I
still think this circuit should be implemented inside TVs ;)
If you are so helpull, could you also help me with something that
*should* be very simple as well ?
I want to connect a LED to my audio cable, that should light stronger
as volume increases, simliar to equalizer - when you hear a shot sound
for example, the LED should flash for a sec. I've seen solutions with
several LEDs and band-filters but I only want one LED. Any thoughts?
 
C

Charles Schuler

Jan 1, 1970
0
KeeperOfLogic said:
Thank you all for your comments. I thought that if freq. filters are so
easy to made, then volume shouldn't be a problem. But I see that there
is a consensus among you about the ineffectiveness of building one. I
still think this circuit should be implemented inside TVs ;)
If you are so helpull, could you also help me with something that
*should* be very simple as well ?
I want to connect a LED to my audio cable, that should light stronger
as volume increases, simliar to equalizer - when you hear a shot sound
for example, the LED should flash for a sec. I've seen solutions with
several LEDs and band-filters but I only want one LED. Any thoughts?

I'd go for a duty-cycle circuit where the on-time of the pulses to the LED
increases as audio volume increases.
 
J

jasen

Jan 1, 1970
0
Hello,
I need a circuit for building a volume low-pass filter. why?
The problem is that every time there is a commercial on TV they
increase the sound level. I want to combat this by building a maximum
sound cap limit (adujstable via Pot.). It should work on all frequency
and should not reduce sound for any db lower then the cap limit.

what you want is called a "compressor", It's a rather complex project,
maybe you can find a kit somewhere?

Bye.
Jasen
 
H

Homer J Simpson

Jan 1, 1970
0
I need a circuit for building a volume low-pass filter. why?
The problem is that every time there is a commercial on TV they
increase the sound level.

There was a "commercial detector" circuit once - might be worth a search.


















....
 
B

Bob Masta

Jan 1, 1970
0
Hello,
I need a circuit for building a volume low-pass filter. why?
The problem is that every time there is a commercial on TV they
increase the sound level. I want to combat this by building a maximum
sound cap limit (adujstable via Pot.). It should work on all frequency
and should not reduce sound for any db lower then the cap limit.
Now the best version of this is that the cap is automaticaly based upon
the avarage volume, so this will work in every sound levels (meaning
cap = normal sound+10db, for example).
But it this is too complicated then a fixed cap with pot. will be
enough.

Since I have only very basic knowledge of electronics, a reference to a
detailed site will be nice.
Thank!

On a related idea, I noticed many years ago that commericals on
standard FM radio tended to be broadcast in mono, whereas
music was in stereo. My thought was to compare the L and R
channels and if they were the same, apply muting. This never
really got off the ground, since I would have to allow for simple
gain differences (balance at the receiver or mismatch in
recording, etc). Plus, all music could be expected to have some
passages that were mostly mono, so there would need to be
some "smarts" and time delays. Nowadays with DSP methods
this might be more approachable, but I wonder if commericals
(radio and TV) are now all in stereo anyway... Just a thought!

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
 
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