Bizarre... I could have sworn that I wrote earlier about the awesome "Levelator" tool from Gigavox, but it appears I did not. In any event, as I was listening to my weekly segment in FIR #190 today, I had to once again praise this wonderful tool. You see, when martyndavies and I were recording the 11-minute segment here in the home studio (during Martyn's trip over here), I did an audio level check, adjusted things, and then started recording. However, we both relaxed a little bit and had a nice chat, but the end result was that levels were very different between us. I mean... you have a loud American who naturally sits very close to the mic and a softer-spoken Brit who sat a bit back from the mic[1]... you are bound to have a problem! And I did... and I wasn't really looking forward to the tweaking I was going to have to do.

However, I exported it out of Audacity as a WAV file, dragged/dropped the WAV file from Windows Explorer onto the Levelator window and went downstairs to get a glass of water. By the time I was back up, my file had been "levelated" and a quick opening into Audacity showed that the levels were now very nice and even. (Export to MP3 and then it was away to Shel and Neville...)

The Levelator truly is an amazing tool, and if you are recording podcasts (or really any other spoken audio) with more than one speaker (especially call-ins, with contributed segments or interviews by things like Skype) you really owe it to yourself to check it out. I think you'll find your audio quality will be dramatically different. (I've been using it for some time now on various podcast files and obviously have been quite impressed.)

Many thanks to Michael Geohegan, Doug Kaye, Paul Figgiani and the other Gigavox team members for making this tool available for the rest of us.

[1] Note to self - I really must get a second mic boom from Heil for times like this when I'm recording with someone else.

Tags: audio, fir, gigavox, levelator, podcasting

After I posted the "Intro to VoIP Security panel podcast, I received a nice note from a listener suggesting that I try a high-pass or notch filter to remove the buzzing that in the podcast.  The note prompted me to investigate further because I, too, had been rather annoyed to have this sound in the recording, especially because I had been recording directly from the conference room mixer!  I heard it while there at the Internet Telephony conference, and tried tweaking the mixer a bit to see if I could drop out the buzz, but found no way to do so and had to conclude that it was originating somewhere in the audio equipment they were using.  So I did really want to get rid of it... but then when I came back wanted to get at least one of the panels out and didn't have time to track down the problem.  But after the comment and before I did the next panel I searched...

...and found in the Audacity wiki - "Eliminating a Continuous High-Pitched Whistle-Like Noise from a Recording", a great little tutorial that helped me figure out what I needed to do.  It involves a few steps, basically:

1. Select part of the recording that is the closest to silence that you can get - where you only hear the buzz.
2. Go to the "Analyze" menu and choose "Plot Spectrum".
3. Identify one of the peaks.
4. Go to the "Effects" menu, choose "Nyquist Prompt" and enter "(notch2 s freq value)" (ex. "(notch2 s 1019 25)")
5. Play the sound and listen for the buzz.
6. If the sound is still there, go back to step #2 and identify another frequency and repeat the process. (writing down the frequencies you are using as you go along)
7. When you have eliminated as much of the buzz as you can, select another segment of sound (preferably several seconds) that includes human voices and repeat step #4 for each of the frequencies you wrote down (unfortunately, per another forum post, there appears to currently be no way to set up a notch filter for several frequencies).
8. Listen to the resulting segment to ensure that it still sounds okay (hopefully sans buzz).
9. Select the entire audio file and apply the notch filters to the entire selection.
10. Listen to your clean(er) audio file.

That's basically what I did... although in thinking about it I might have had a step between 8 and 9 where I used "Undo" to remove the notch filters on the small human voice segment before applying the filters across the entire file.  For my own record, here's the sequence I did:

(notch s 1019 25)
(notch s 2046 25)
(notch s 21649 25)
(notch s 21650 25)
(notch s 21652 25)

That all seemed to do the trick. There still a bit of a low hum, but I also tried a high-pass filter that would basically wipe out everything under a certain threshold, but using numbers down like 100Hz I didn't discern any real difference - and I was reluctant to go too much higher and start impacting voices.

Anyway, you can hear the difference on the "VoIP Security Best Practices" panel.  Still a small buzz... but at least the high-pitched one is gone.  (And suggestions on killing the low buzz are always welcome. :-)

Tags: audacity, audio, podcasting, post-production

When I am in a hotel room, I want to listen to podcasts, but I don't want to use earbuds - nor do I want to use my computer speakers. However, many of the portable speakers out there specifically designed for the iPod suffer from one basic failure - they aren't designed to be tossed in luggage! Generally, the speakers have been exposed, or the controls, or both.

Enter the JBL "On Tour" portable speaker unit. It's a sweet little unit that has a metal cover that slides over the speakers, controls and jacks when closed up, so it's perfect for putting into your laptop carry-on bag. Slide the lid back and you've got a nice speaker set. It can run off of 4 AAA batteries for true portability - or work perfectly fine with the supplied AC adapter. It also just takes a standard 1/8" jack, so you can plug anything into it. Of course you can plug your iPod or other player in, but I have sometimes just plugged my laptop into it for better sound quality. It comes with a 1/8" to 1/8" cable, as well as a second cable with a mini plug on it that, I guess, could go into a cell phone or something else with a smaller jack.

All in all quite a nice unit for listening to podcasts on the road. You can also check out reviews at PC Magazine and The Gadgeteer. P.S. Although all the pictures show it as silver, the one I bought at some local store was actually black with silver ends, so other options may be available.

Tags: audio, jbl, podcasting

For quite some time, I've been looking to get a "microphone flag" to put on my handheld mic for when I'm doing interviews at conferences and trade shows. I think it just looks that much more professional (especially on a trade show floor) and it's been on my "to do" list since I went to the Podcast Academy 2 in Boston earlier this year.  This was reinforced by my trip to the Podcast Expo last weekend and, given that I'm heading out to the Internet Telephony conference in San Diego next week, I thought I'd see what was involved.

Obviously, "time", for one thing, if you want a decent quality mic flag.  Out at PME, several people warned me away from the blank ones that you simply print out stickers and put them on.  Still, I was going to try to order a blank one from B&H for delivery Monday so that I could have something for when I leave on Tuesday.  However, just my luck, B&H is shutting down for a one-week holiday and stopped taking orders last night at 11pm!

In the meantime, though, I found Michael Geoghegan's blog entry on the topic pointing to a podcast episode with Glenn Love of Impact PBS.  Paul Figgiani (of Podcast Rigs) had also pointed me to the company as well.  They aren't cheap (about $60 for 1 mic flag), but have seen some of their flags out at PME, I'll definitely agree the quality is there.  It's definitely something I'll check out.  (And as far as the time, it seems it will take 7-10 days to get one from the time the artwork is approved. This is similar to what other vendors are offering.)

Tags: audio, micflags, podcasting

Had a bit of trouble today when I went to upload a new Blue Box episode.  It sounded fine when you downloaded and played it, but when you used the flash-based player I have on the site, it sounded like we were a bunch of chipmunks!

It turns out in reading through the LibSyn support forums (because I was thinking of switching to using the LibSyn flash player instead of the one I use now) that the issue is with the sampling rate in the MP3 export rate out of Audacity and LAME.  Sure enough, I looked in iTunes and my freshly-exported MP3 file had a sample rate of 24Khz versus the standard 44.1Khz.  What happened?

Well, it turns out that Audacity lets the LAME encoder control the sampling rate! You can set the bit rate in Audacity, but Audacity lets LAME adjust the sampling rate.  I never had this issue before because I've always used the default bit rate of 128Kbps, which must just use the default sampling rate. However, as I wrote earlier, I'm looking to use a bit rate of 56 to get much smaller file sizes.  This was my first upload at the new bit rate.

Only way I could work around this right now was to go to the command line to force an output sampling rate of 44.1:

lame.exe -b 56 --resample 44.1 inputfile.wav outputfile.mp3

Ta da... an MP3 file that plays well in the flash MP3 player!  Just had to delete the old one on LibSyn and upload a new one... hopefully I didn't delete the old one while someone was in the middle of downloading (but I probably did).

Ah, the fun of all these different audio issues... :-(

Tags: audacity, audio, lame, mp3, podcasting

One of the things that had continued to puzzle me was why Shel Holtz was able to get the FIR podcast audio files to be so much smaller than the audio files I was getting for Blue Box.  I knew that he used the same tools as I do - Audacity and the LAME MP3 encoder - but yet my files were averaging around roughly 1MB per minute and his were half that, i.e. a 10 minute podcast for me would result in a 10 MB MP3 file while for Shel it would be 5 MB (not that either Shel or I really ever produce a podcast as small as 10 minutes!).

Yesterday in the midst of some other things I fired Shel a message and he clued me into the one setting that is different between us.  I had the bit rate for MP3 export set to 128... and he had it set to 56.

Ta da... one little change and now my audio files are about half the size!  (Hmmm... I wonder if I set it to 64, would they be exactly half the size?)  On a quick listen, I can't really hear any difference between the two files (one exported at a bit rate of 128 and one at a bit rate of 56).  Given that our show is a talk show, we don't necessarily need the audio quality of a music podcast.  I'll have to export the next Blue Box episode at that bit rate and see if anyone has any comments.

Note: Here's a nice little piece in Podcasting News that talks a bit about adjusting the bit rate and gives some samples recorded at different rates.

Tags: audacity, audio, fir, podcasting

Shortly before leaving for Montreal, I picked up an iRiver T30 portable MP3 player/recorder to use for quick recording and recording where I don't need the higher quality recording I can get out of my Marantz PMD-660, which I also have along with me. It will be interesting to see how this unit picks up sound.

The main reason I got the unit, actually, was for hallway interviews or, for instance, when I go on the cruise boat tomorrow night for the social. The PMD-660 is just far too big to carry with me. This T-30 is basically un-noticeable sitting in my pocket. It's small size is wonderful.

Tags: audio, ietf, ietf66, iriver, podcasting

Neville Hobson has a good thread going on right now about the M-Audio Microtrack 24/96 over on his blog.  I've been very intrigued with this device ever since I saw Mikey from Pulver Podcasting Network using it to record their shows out at VON in San Jose earlier this year. Shel Holtz has also been raving about it since he picked one up a month or two ago.

Here's my dilemma. For most of a year, I've been using a Marantz PMD-660 for portable recording, but it is just too darn big for many events.  I can't just stick it in my jacket pocket... or easily pass it around to people.  I want something smaller.  So I've been thinking about this M-Audio device... or an iRiver.  The issue with the iRiver is that it can't do WAV and doesn't have all the more "professional" recording settings I've been enjoying using on the Marantz.

My major sticking point with the Microtrack is the fact that it doesn't have built-in microphones... you have to carry the "T" microphone unit with you... and I can just see me forgetting it sometime when I absolutely needed it.  I don't know, though... it sure is tempting... :-)

Tags: audio, m-audio, marantz

I've had my desktop PC for, I don't know, 3 or 4 years, and while it isn't a powerhorse (2Ghz Pentium, 1 GB of RAM), it was always sufficient for the type of things I do at home... email, web-browsing, writing, taxes, the occasional spreadsheet... and its 80 GB disk drive seemed quite vacant and not in any danger of reaching capacity any time soon.  I rather expected that I'd keep on using the machine for quite some time without needing to enhance it.

Then I started podcasting.

Oops.  One thing about audio files... they are not small!  Take, for instance, the last show.  The final MP3 file only comes in at around 42 MB.  But the original recording in Audacity came in at a whopping 586 MB!  To make matters worse, because I'm paranoid and extra careful, I always make a "edit" version of a show where I do the actual post-production.  It's basically the same size... so you wind up with 1 GB for the show - and it was actually one of the smaller shows!

Doesn't take too many of those to start filling up a hard drive.  So tonight was a night of moving all the old shows over onto a portable (USB) hard drive to free up space.  And I've already got my eye on a PC that has both larger drives - and also will be whisper-quiet... :-)

Tags: audio

In my ever-present quest to improve the audio quality of Blue Box it recently occurred to me that I might be able to further reduce some noise by moving from using my laptop's built-in soundcard (of questionable quality) to an offboard USB sound card. After much research, I settled on the Edirol UA-1EX, primarily because it's very small and compact and can travel well with the laptop. Unfortunately, after installing it, I could find no way to easily control the output volume. There's a wheel on the device to control the input volume - and a wheel to control the output headphone volume - but not the main output volume. Plus, when you use the device in its default "Advanced" driver mode, the Windows volume control no longer works!

My inability to control the volume probably wouldn't have been a problem except that when I plugged the card into my mixer, the volume was unacceptably low. No matter what I did, I couldn't get adequate volume. So, frustrated on both accords, I posted my dilemma to the Podcastrigs forums, where, as usual, Paul Figgiani provided a prompt response which helped point me in the right direction. In the end, I have the problem solved to a degree - although I'm no longer using the Advanced driver and so I do have Windows volume control. Fun, fun, fun...

Tags: audio, edirol, podcasting, podcastrigs

In working with Audacity and needing to fade a section of a podcast but not wanting to fade to zero (which could easily be accomplished by Effects->Fade out...), I stumbled upon this great tutorial which introduced me to the truly wonderful envelope tool.  What a truly awesome tool!  Fantastically easy way to fade things... but even more so to adjust gain when you have a very varied recording.  I've already received the comment that Jonathan's voice was much better on our latest podcast (#6) and part of that is the method we used for communicating, but part of that is also that I used this tool to raise the places where his voice was low.

Very cool tool!  And thanks to the transom.org folks (whomever exactly they may be) for creating this tutorial... I'm checking out more of their site as well.

Tags: audacity, audio, podcasting
Current Mood: impressed

After hearing Shel Holtz rave (on For Immediate Release) a couple of times about his Marantz PMD660 portable recorder and after a couple of late-night hours of reading online reviews and information, I broke down and purchased one along with a nice Shure microphone on Friday.  After a couple of days of trying it, all I can say is that it is one sweet little piece of electronics!  What's amusing on one level is that it's almost the size of one of the old portable tape recorders (well, a little smaller), but it can do so much more.

I'm very much looking forward to giving it a test this week down at VON with some recording I want to do.

Tags: audio, podcasting

Just stumbled upon the fact that a month ago, July 14, 2005, the use of the ".mp3" extension was ten years old.  And how little did all those engineers know what a fundamental difference that audio format would make...

Tags: audio