Podcast Noise Reduction Example – Cyber Speak

Good noise reduction when editing a podcast is an important skill.


I received a vocal track for Cyber Speak (http://cyberspeak.libsyn.com). Bret’s voice is nice and clear itself. But his new recording environment put a low level of constant background noise into his track. So I pretty much pulled it all out completely leaving just his voice. This worked well because his voice was so strong over the noise. I stacked Soundsoap doing general broadband reduction making sure to adjust the settings so it did not noticeably distort Bret’s voice. That pulled a lot of the noise out or at least down. The problem is I always do RMS leveling on the voice tracks as I have mentioned in a previous post. So if noise is still present you amplify it too. So I stacked one more effect. I used the built in noise reduction for soundtrack pro. The trick was adjusting the threshold up high enough to catch most of the noise floor while relying on Bret’s voice volume to protect it from the reduction. It worked like a charm. See the before and after images below. I show both waveform and frequency views.


This is exactly why I recommend folks record five seconds of “silence” when they start recording. It gives you a nice region to sample noise for good reduction.


If you are curious to hear the final result check out the Nov 21 Episode of Cyber Speak.


OWLE Bubo for iPhone

I got my Owle Bubo (http://www.wantowle.com/) today.  It is a limited edition run and mine is 233/500.


It is very well designed.  Nothing blocks the dock connector so I can plug in my iPhone without removing it from the chassis.  The included mic comes in a nice little velvet pouch and is very sturdy.  It just plugs into the headphone/mic jack and a hinge lets you aim it to the front of the unit so your sound comes from where the lens is pointed.


Now to just get myself a nice LED light with the shoe mount that is on top of the Owle.



Logging – Collecting Mac logs to your Logging VM

Perhaps you have made yourself a logging vm, or even a logging machine out of an old laptop using my pdf instructions.  At home I actually turned a real old IBM Thinkpad A22m into a unbuntu logging machine.  Just like my directions only no vmware.

I send all my network hardware logs via syslog to the machine.  BUT I also did one simple change to the syslog.conf on every mac in my house.  Now all my mac logs collect into my machine for searching in Splunk.

  1. Just open Terminal on your mac.
  2. sudo vi /etc/syslog.conf
  3. edit the file and add the following line, substituting your own logging machine IP address.
    *.*               @loggingmachineipaddress
  4. Make sure to use an actual ip address in place of loggingmachineipaddress.  I tried using the bonjour or mdns name like logger.local and my macs never consistently sent logs.  So changing to IP address it seemed to work after that.
  5. Next if you are in Leopard you can do the following two terminal commands to restart syslog and pick up the config change.  Otherwise you could also just reboot your mac.
  6. sudo launchctl unload /System/Library/LaunchDaemons/com.apple.syslogd.plist
  7. sudo launchctl load /System/Library/LaunchDaemons/com.apple.syslogd.plist

Building a logging VM – syslog-ng and Splunk

Recently I wanted to build a log collection virtual machine.  I settled on a combination of syslog-ng and splunk.  Syslog-ng lets you do filtering, message rewriting and routing to multiple destination types.  Splunk v4 gives you a nice ability to search the gathered logs.  So you can follow my two documents.  The roll your own covers the building of the vm.  The getting started covers doing the last setup tweak to use and collect certain event types I decided would make a good stating example set.

We use Ubuntu sever 32bit 9.10 with syslog-ng v3 and splunk v4 in this tutorial.  I built mine in vmware fusion on my mac.  But you should be able to adapt to your own box/virtualization of choice.


Logging – syslog-ng rewrite kiwiSyslog forwards

Lately I have been working on making a vmware virtual machine for combining syslog-ng version 3 and splunk.  I wanted to leverage syslog-ng for routing of messages and for rewriting messages from an existing kiwisyslog server.

Let’s say you have all your network gear sending events to an existing kiwisyslog install.  You can add an action to foward the messages and include the original source IP.  The problem is that the original IP becomes part of the message.  When it reaches splunk you would rather it see the messages as having come from the original host so you get the best mapping to host fields in splunk searches.

So we use syslog-ng to receive the forwarded messages then rewrite the message before it is picked up by splunk.  We tell syslog-ng to listen on udp port 3514.  This is the port we tell kiwisyslog to forward events to.  Next we tell syslog-ng to write the events to a fifo linux queue while applying the rewrite.  It is easy from there to tell splunk to pull events from the fifo.

So click more to see the config I used in syslog-ng to make this work.  The solution is a combination of telling syslog-ng to NOT parse the incoming messages then to apply the rewrite rule.  I do plan on writing a pdf guide on building the logging vm from scratch soon.  But for now you can check out the config below.

Continue reading “Logging – syslog-ng rewrite kiwiSyslog forwards”


Simple podcast audio level steps.

Want to make a nice consistent level in your podcast production? Here are the simple steps if your software supports RMS and Peak leveling. These steps come from a ot of experience and guidance over the years from my friends Victor Cajiao and Paul Figgiani.


1. Record as clean audio as you can (minimal noise).
2. Do any noise reduction. This is so you do the least reduction BEFORE you start raising levels.
3. RMS level the track to something around -17.5dB. I actually use -13.1 for Cyberspeak because their mic levels match up the best here.
4. When done editing your show, mix down then Peak level to -1.0dB


That should do it. Now if you don’t have RMS leveling ability you can always use the free Levelator. Just remember. Do your noise reduction if any BEFORE you adjust levels. This increases the chance you pull the noise so far down it doesn’t also get amplified.