making podcasts easier to hear with dynamic compression

August 14, 2008 2:02 AM

Can I make podcasts easier to listen to in a noisy environment using compression?

Calling all audio folks... I have a collection of podcasts (currently working my way through TED) to listen to on my boring commute, either by motorbike or car, both of which are quite noisy. Obviously I don't just want to crank up the volume on my mp3 player, for fear of damaging my hearing. So I'm wondering if I could use compression (of the dynamic kind, not the wav->mp3 file size kind) to even out the volume throughout each track and therefore make it easier to hear what's being said at a lower volume. This would be particularly useful where there are multiple people talking with different voices (e.g. radio 4's In Our Time, another current favourite). Will this work?

posted by primer_dimer to technology (9 comments total)

It would probably help-- though the compressed tracks will sound worse in a quiet listening situation. And keep in mind that you'll be amplifying and re-encoding the mp3 artifacts, so save them at a higher bitrate if you can.

The free audio editing program Audacity has a built-in compressor. Try a ratio between 4:1 and 8:1. Set the threshold to a value about 6 dB under the peak values of the quietest voice. Keep the attack and decay on the short side. Start there and then mess around with it.
posted by scose at 3:06 AM on August 14, 2008 [1 favorite has favorites]

What kind of headphones are you using? I used to walk to work next to a busy road, and I had my headphones at full volume - and even that wasn't enough. In a normal environment, full volume was painful.

I bought some of the plug style headphones, which actually sit inside your ear with a rubber part, and stop external sound getting in, and found that I could listen at a sensible and safe volume. The standard earbud or external headphones were just no good in that noisy environment.
posted by tomble at 3:50 AM on August 14, 2008

Headphones on a bike? That sounds even more dangerous that headphones in a car.

I wonder what would happen if you added a touch of compression then mixed in some white noise in the background. That should really isolate you from your environment!
posted by Leon at 4:14 AM on August 14, 2008

Noise-cancelling headphones will help you hear your podcasts on the bike; probably illegal in the car.
posted by flabdablet at 4:23 AM on August 14, 2008

What you'll want to do is run the audio files you're listening to through a basic audio editor. Audacity is a great free one (although you'll need to grab the MP3 encoding libraries before you begin) and do what is called "normalizing". This will bring up the audio from the podcast to a more consistent volume. That should help you not be deafened by those who speak louder than others when listening in areas with a lot of ambient noise.

You can grab Audacity from audacity.sourceforge.net
posted by cgomez at 6:01 AM on August 14, 2008

Apologies for the derail, but could I echo Leon's point that listening to anything with headphones on a motorcycle (or a bicycle, so far as that goes) is a Really, Really Bad Idea.

When you're riding, you need to pay attention every minute of every ride, anticipating intersection and other merge problems, if you're in a cager's blind spot, edge traps and other road surface problems, etc. Further, getting cut off from possible auditory warnings doesn't sound smart to me either.

I listen to podcasts (recommendations: Filmspotting; Bloggingheads; New Yorker Out Loud) all the time on the road, but I do it in my car, surrounded by crush zones and air bags.
posted by mojohand at 6:55 AM on August 14, 2008

I listen to podcasts in one ear while riding my bike in NYC and have a similar problem. Particularly with NPR podcasts which don't seem to be very loud.

The solution that I found was to use the more 'plug' type headphones, as tomble said, and I have used the relatively cheap Sony MDR-EX51s, though you don't want the white ones, because they melt. However, even in one ear, sometimes the isolation can lead to a "deaf" feeling in that ear - deaf to the sounds of cars and pedestrians that I can usually hear through non-plug style phones...
posted by SmileyChewtrain at 7:03 AM on August 14, 2008

And to further echo Leon and mojohand - I usually pull it out of my ear when I'm in a heavy traffic area, it's too confusing and hard to pay attention to possible deathtraps.
posted by SmileyChewtrain at 7:05 AM on August 14, 2008

I do the same thing, listening to podcasts in my noisy truck on long drives, but through the speaker, not earphones, and I have the same problem. I found that compression makes a BIG difference in understandability of spoken words.

Meet the Levelator, which was developed for this very purpose. It compresses, normalizes, and limits the audio level. It's a free download, for Windows/Mac/Linux, drag-and-drop your audio file. The only real limitation is that it accepts WAV and AIFF files, not MP3. I like it.
posted by exphysicist345 at 8:02 PM on August 14, 2008