I have mp3 files which trigger some protection circuitry of an amplifier, turning off volume for 3 seconds and restart file. To avoid the pause and restart I must run the file in too low volume of overall sound. I need a process to find such peaks automatically and reduce them. (I can repeat the process until I find a suitable setting). When done I intend to “normalize” all the files on USB stick and export mp3. I have not used Audacity for a few years but still feel comfortable with its basic operation. There may be new menus / tools suitable for this case of which I need help how to do. I did not find anything on the forum reflecting what I need. Thanks for helping. (audacity on win10)
Audcaity’s built-in Limiter is what you’re looking for, (without make-up gain).
other similar effects are available as plugins …
It MIGHT not be the momentary peaks which don’t necessarily sound that loud or over-stress your amplifier or speakers.
Limiting MAY not help and it MIGHT make the problem worse, if you turn-up the volume from where it is now!
Does your amplifier have enough air circulation? It’s usually heat that shuts down an amplifier and short-term peaks don’t cause much additional heat. The heat inside the amplifier also depends on the ambient temperature, how long the amplifier has been on, and how long it’s been over-stressed,.
…The CORRECT solution is probably a “bigger” or better amplifier, and of course your speakers have to able to handle the wattage too.
Or, turn just down the volume! 
Regular normalization is PEAK normalization. Usually, the peaks are normalized/maximized to 0dB, but with Audacity you can choose a different peak. If the peaks are causing the problem and you keep the volume down that should prevent it, but most commercial recordings are already 0dB normalized.
The peaks don’t correlate well with perceived loudness, but Audacity also has Loudness Normalization which DOES try to match perceived loudness. However, it can end-up pushing the peaks over 0dB so you have to “be careful”.
A couple of other loudness matching options are ReplayGain if your player supports it. Or Apple has something similar called Sound Check. These don’t “touch” the actual audio data but they tag the file and the player adjusts volume just-before playback starts.
Or there is Mp3Gain which adjusts the loudness of the acual MP3 so it “works everywhere”.
By default, none of those won’t push the peaks over 0dB, so you still end-up with some quieter-sounding tracks but they will be boosted as much as possible without clipping.
Because most commercial tracks are already 0dB peak normalized (including the quiet-sounding tracks that can’t be boosted without clipping) ALL of these loudness-matching methods tend to lower the volume of most tracks. That bothers some people, but it’s not a problem if you’ve got enough amplifier gain.
Some notes about MP3 -
As you probably know, MP3 is lossy compression. Information is thrown-away to make a smaller file. When you open an MP3 in Audacity or any normal audio editor it gets decompressed. If you re-export as MP3 you are going through another generation of lossy compression and some damage accumulates. You may not hear any quality loss but it’s something to be aware of and you should try to minimize the number of times it’s compressed-recompressed.
ReplayGain doesn’t decompress, or even “touch” the actual audio and Mp3Gain uses a “trick” of changing something in the file headers so it doesn’t decompress or change the audio quality.
Another side effect of MP3 is that it changes the wave shape making some peaks higher and some lower. If you peak-normalize at 0dB, the exported MP3 will usually go over 0dB. Some people normalize to -1 or -2dB to prevent that… Most of my MP3s were ripped from CD, and since many of the CDs were 0dB normalized the MP3s often “show red” (potential clipping) when opened in Audacity.
CDs and regular WAV files are hard-limited to 0dB and you’ll get clipping (distortion) if you “try” to go over. MP3 can go over 0dB without clipping but your DAC (digital-to-analog converter) is limited to 0dB and you’ll clip your DAC if you play it at “full digital volume”. (I don’t worry about it too much because I don’t think the slight clipping is audible, and MP3 is already lossy anyway.)
thank you, I’ll try soft limit, It looks like the best for my case.
thanks, had I known the amp/speaker (KSR) had this interruption problem I would not have bought it. It is not mentioned in the sales literature. To buy another unit may be luck or waste of money. It is already the 2nd unit, the 1st was bad design too, but with different spec’s.
I’ll try soft clipping. once this sounds good I’ll normalize to set all the various USB mp3 memories to the same level, this will make operating them much easier as the volumes will be similar for the similar music.
I have an additional question: After looking at one of the files which triggers the volume protector I see a few needles in the full size 3 min audio. In order to get a feeling of how much I need to adjust (soft Limit) I would like to view several peaks close up. Is there such a peek search tool which allows me to jump to the next, forward backward? In place of using the expansion and my eyes, which would be rather tedious. How to set the “finder”?
{Insert: Years ago I removed “knaks” of such a display, which resulted from the vinyl transfer to digital. I manually reformed the peaks, too much work really. End of insert.}
I tried to add this text to the original post, the “pen” did not allow writing.
I know about the zooming. Full view might not show all the peaks, depends how A. is programmed. I was hoping to step from peak to peak, without searching it manually.
I shall try Label Sounds - Audacity Manual
thanks for the pointer.
I tried both, normalization & compression and soft limit. The limit picture on screen looked better. I processed 34 mp3 files. When I tried the result on a location where I can turn up the volume I found the situation had hardly changed. My perception was I could have just a little more volume from these files. The volume from the built in radio is much higher, it meets expectations. Hence the amp’s behavior is still next to useless. The same bad way on AUX input. The manufacturer’s rep in country does not respond. I found not a single information on the internet about the matter. I can only warn folks never to buy KSR KAISER audio equipment. Side note: Sales literature claims 12 V= external power can be used. Buy it, read the manual you find the device may not be turned on while charged from a 12V source. It is worse than bad. I think I end here, thanks for your assistance.
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