I find that threatening to remove the MP3 player from my Child for a month 
if I find him playing it above the agreed volume works wonders.

He only did it once before he learned his lesson.

Dom
----- Original Message ----- 
From: "Ariel Rocholl" <foros@arocholl.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Friday, March 07, 2008 5:53 PM
Subject: [EE] Audio Headphone limiter / normalizer


>I ran in a couple of situations in which I noticed my kid was not
> using headphones at a safe listening level, so I am a bit worried
> about it. Therefore I tried to find something already available in the
> market and, besides the feature offered by the iPod for parents
> limiting the sound level, I found no general device to passively nor
> actively limiting the audio levels automatically for a device. So my
> first question is if anyone knows a commercial device I can connect
> between the audio output of any gadget and the headphone to limit it
> to a value of my interest, regardless of the output level of the
> gadget itself.
>
> Assuming such a device doesn't exist, for a DIY project what I did
> found was sound "clippers" and "audio limiters" but for a very
> different purpose: remove glitches or high spureous from a signal, by
> limiting them with two germanium diodes antiparalell or similar
> circuit (in some cases with more sophisticated variations of the same
> idea), see for instance
> http://www.headwize.com/projects/limiter_prj.htm
>
> But those clippers do not exactly avoid a high sound level by
> downsizing the audio wave, it just clips the wave amplitud when it is
> higher than certain thresold. What I need is really more like a
> variable gain amplifier that adjust the input signal and amplifies it
> only till certain point, depending on the output level but never
> really clips it. Furthermore, an ideal design should take into account
> external noise level, to let "safe thresold" to be a bit higher on
> noisy environment, but lower on quiet environment.
>
> Probably a DSP could do the job, but may be a little overkill. What
> about a programable gain amplifier driven by a PIC with a comparator
> that looks for signal level integrating every second or so, and then
> adjust the PGA according to that?
>
> TIA
> -- 
> Ariel Rocholl
> Madrid, Spain
> -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.516 / Virus Database: 269.21.6/1316 - Release Date: 
> 06/03/2008 18:58
>
> 

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist