Automatic Television Commercial Volume Limiter/Regulator

[audioguru]

First you need to analyse the audio on an oscilloscope to see if the peaks are at the same level like I think they are. If the peaks are too loud then the FM will be over-modulated and cause severe distortion. Maybe you are watching digital stations that do not control the max volume. The TV stations I watch do not cause the same problem as yours.

 

[arizonaguide]

YES! I think my next step is to get a good stereo microphone in my TV room and record the typical show to commercial transistion to an MP3 file, then take a look at the waveforms in a sound editing software and find out EXACTLY what the waveforms look like.

Perhaps THAT is another solution:
Run all the CABLEBOX OUT stereo through my computer before sending it to my BOSE AUDIO SYSTEM BOX INPUTS, and use some type of software program to "monitor and normalize" the stereo signal.

I ALSO like the idea of "hacking" the ALC Circuit. (Automatic Level Control) from an old cassette recorder!

One way or the other I'm gonna put an end to that TRIPLE VOLUME (anger and discomfort) at MY house!

BTW, MERRY CHRISTMAS, Folks!!!

 

[gary350]

This has been regulated by Federal Law since about 1970. I remember when I was taking electronic is college we learned why advertisements on TV sounds so much louder than the TV shows. You are right use a scope to look at the signals to see if they are different. Technology has come a long way since I was in school I always figured a compressor would work for this project but I never built one and tried it. I bet there is a better way now with lots of new technology that was not available in 1970.

 

[k7elp60]

My hearing for frequencies above about 1500Hz is very close to 60db below normal so watching TV with the wife was a problem for her in that the volume had to be quite loud for her and I could not hear some audio or it was not clear.
I built the attached circuit. The SA571 is a compressor that keeps the audio level pretty constant. One section of the TS972 op amp is a voltage detector that turned on an LED to let me know the voltage of the 9V battery was low.

As I recall the SA571 is dual channel and I am only using one channel. Since I use headphones, they are wired in parallel.

 

[audioguru]

I had a Toshiba TV that had ALC.
When the program sound was at a low volume then the TV slowly boosted it until the backgriund sounds were much too loud. Then when a loud sound came its first few hundred milli-seconds were blasting loud until the circuit could reduce the volume. Each loud sound was like a huge hammer hitting my head. It was absolutely useless.

 

[GJS]

obviously, this is an electronics forum but lawmakers are trying to address the problem:
**broken link removed**

it is VERY annoying!

 

[arizonaguide]

Man, you both are right on the money.

In order for me to follow the dialog of the TV show, I have to have it louder than the wife likes. Not because of lack of volume, but because the surround sound DROWNS out the voice tract. I cant hear the freakin talking because the damn city bus (or whatever) in the background is so loud in relation to the voice tract. If I can amlify just the voice track, it would help watch the TV show a lot! I already have the voilume up pretty loud...and STILL can't make out WTF they are saying!

Then if the characters have a thick Bronx or Boston accent, it's almost hopeless (I'm from out West)...and the subtitles for the hearing impaired has to get turned on (and I may just go to this and mute the program entirely if I can't find a solution!).

I asked the BOSE people about this problem, and they told me to raise the volume on the center speaker...and to reduce the volume on the surround speakers. I guess it's common for the voice track to be on the CENTER channel or whatever. Anyway, I did this, and it didn't help much.

So, to hear the voice track in all the surround sound noise I have to have the normal volume pretty loud.

THEN, when the commercial comes on at TRIPLE that loudness...it damn near BREAKS WINDOWS, and sends my wife running from the room!!! And, I have to try to scramble for the remote (in the dark) to MUTE it before windows break...and I always hear a comment muttered under my wifes breath about my hearing problem and the loud commercials.

I'm beginning to think that the Computer audio card itself, combined with some active "monitoring and normalizing" software, may have a solution.

 

[chemelec]

Possibly Check out this one:

**broken link removed**

And Maxim usually gives Free Samples.

 

[audioguru]

I think the movie producer has read and seen the program's text so many times during rehearsals that he doesn't listen to it anymore which allows background sounds to be too loud.

Maybe your center channel did not produce only voices because the show was not made with surround sound or because your amplifier is not switched for surround sound.

 

[arizonaguide]

Yes, that could be.

But, I WILL come up with a solution though, because my marriage is too darn GOOD to let this continue to be a sore point...not to mention that it USED to be against the law for the unethical advertizers to pull that crap. And, the anger that washes over me everytime I have to fumble for the mute button can't be good for my health.

I know that with some help from the smart folks here, many of which seem to share the same problem (Cheers, K7elp60!), that we can come up with a solution. What an amazing site this is!
I'm making it my News Years Resolution!

 

[audioguru]

Make a guess about how much compression was used.
Then make an expander with the opposite.
Then make a peak limiter circuit reduce the peak level.

 

[arizonaguide]

Might be easier to just lobby congress!

 

[gary350]

obviously, this is an electronics forum but lawmakers are trying to address the problem:
**broken link removed**

it is VERY annoying!

This is an excellent opportunity for someone to start their own business making and selling TV compressors. I can list 30 people that hate the loud advertisements on TV an I bet you can too. I bet everyone in the USA would buy one if it was available or already installed on a TV. I bet you could start a TV service that installs compressors as a full time business. Once the word got out you wouldn't be able to keep up with demands.

 

[audioguru]

This is an excellent opportunity for someone to start their own business making and selling TV compressors.

You do not want a compressor. The "too loud" problem is caused by a compressor that limits the peak volume then boosts the average volume.

Instead you need the opposite of a compressor that is called an expander that makes the sound normal, then an automatic volume control circuit can detect the peak volume and reduce the overall volume if it is too high.

 

[mbarazeen]

i think a short of AGC (automatic gain controller) is required to do this job.
you can have a set control for the gain on the Amp box.
the circuit will over see the peak out power and set the out put gain to get the peak of out put not to exceed the set value.

now your volume can only be controlled by this external knob, not by your remote...

 

[gary350]

You do not want a compressor. The "too loud" problem is caused by a compressor that limits the peak volume then boosts the average volume.

Instead you need the opposite of a compressor that is called an expander that makes the sound normal, then an automatic volume control circuit can detect the peak volume and reduce the overall volume if it is too high.

I guess I just don't understand how the sound works on the new TVs these days. Can you explain this better. How about some graphs or sin wave scope drawing of something so it makes sense. If I still owned a scope I could take a look and see what is going on.

Today I am building a dual volume control to head phones for the TV so I can turn the volume up to 120 db for left ear and 60 db for right ear so I can hear the TV. I have this idea that a fairly large electrolitic capacitor may level out the loud volume on the advertisements. I will give it a try to see what happens.

 

[audioguru]

A capacitor will not level out audio volume changes.
You must rectify the signal then quickly charge a capacitor to the peak voltage of the signal. The capacitor voltage controls a Jfet attenuator in an amplifier circuit.
The higher is the peak signal level then the higher is the capacitor voltage then the higher is the amount of attenuation.

But it responds to the peak level, not the average level so compressed and non-compressed sounds will be controlled the same because their peak levels are the same. The compressed signal will sound much louder because its average volume is louder.

If you make an averaging circuit then it will respond slowly and let very loud sounds at the beginning of each word or sound go through.

 

[arizonaguide]

So, to my understanding the commercial's sound waveform(s) isn't any taller in amplitude than the loud parts of the show itself, it's just fatter for a given sound...so the "average" effective volume is louder ? In other words the sounds waveform is short enough to be within the "legal" limits, but fatter.

Do I understand that correctly?

If that's the case...then that's what confuses me.
Because that would change the frequency of that given sound, wouldn't it?
So the whole "compressed" concept really throws me.

Time to do a Wikipedia search on "compressed audio".

 

[arizonaguide]

I guess it's actually called Dynamic Range Compression...

Dynamic range compression, also called DRC (often seen in DVD and car CD player settings) or simply compression, is a process that reduces the dynamic range of an audio signal. Compression is used during sound recording, live sound reinforcement, and broadcasting to control the level of audio. A compressor is the device used to apply compression.

Dynamic range compression should not be confused with audio data compression which is the process of making audio data files smaller. Both dynamic range and data compression are often called simply "compression."

In simple terms, a compressor is an automatic volume control. Loud sounds over a certain threshold are reduced in level while quiet sounds remain untreated. This is known as downward compression, while the less common[citation needed] upward compression involves making sounds below the threshold louder while the louder passages remain unchanged. In this way it reduces the dynamic range of an audio signal. This may be done for aesthetic reasons, to deal with technical limitations of audio equipment, or to improve audibility of audio in noisy environments.

In a noisy environment, background noise can overpower quiet sounds (such as listening to a car stereo while driving). A comfortable listening level for loud sounds makes the quiet sounds inaudible below the noise; a comfortable listening level for quiet sounds makes the loud sounds too loud. Compression is used in order to make both the soft and loud parts of a sound more tolerable at the same volume setting.

Compression reduces the level of the loud sounds, but not the quiet sounds; thus, the level can be raised to a point where the quiet sounds are more audible without the loud sounds being too loud. Contrast this with the complementary process of an expander, which performs almost the exact opposite function of a compressor, i.e., an expander increases the dynamic range of the audio signal.[1]

A compressor reduces the level of an audio signal if its amplitude exceeds a certain threshold. The amount of gain reduction is determined by a ratio. For example, with a ratio of 4:1, when the (time averaged) input level is 4 dB over the threshold, the output signal level will be 1 dB over the threshold. The gain (level) has been reduced by 3 dB. When the input level is 8 dB above the threshold, the output level will be 2 dB; a 6 dB gain reduction.

A more specific example for a 4:1 ratio:

Threshold = −10 dB
Input = −6 dB (4 dB above the threshold)
Output = −9 dB (1 dB above the threshold)

https://en.wikipedia.org/wiki/Dynamic_range_compression

STILL kinda confuses me wrapping my mind around this, and as to the solution. I guess I need to understand the concept of "gain" a bit better.

 

[audioguru]

An audio compressor "squashes" the amplitude of the peaks then amplifies the entire signal so that the squashed peaks are at the same level as before. Then the average level is boosted and it sounds much louder.