Audio recording questions and updates from class

Hi all,

This is Andy, also known as "A7". There were a few unreolved questions and issues that arose in class. After a bit of playing around on my PowerMac at home, I came across a few answers. I thought this might be helpful to others, so here's some technical info for those interested.

Q1- Where is the built-in microphone on the PowerMacs (like in the lab)?

A1- There is none! The PowerMac line does NOT feature a built in microphone. You must use an external microphone plugged into the lower audio jack at the back of the machine. Another option is to record on an external device (minidisc, tape, mp3 recorder) and input it either digitally (USB cable) or as audio (line in or optical digital in). All other Macs, including iMac, eMac, iBook and Powerbook (unsure about Mac mini), all have built in mics.

Q2- How do you convert a "song" (series of audio recordings) in GarageBand to mp3 format?

A2 - As mentioned in class, you must use "export to iTunes" from the file menu in GarageBand. However, this does not export as an AAC or MP3 file. The file is exported to iTunes in an AIF file format (no compression). If you have already set your importing options in iTunes to import to mp3, then you need to highlight the song in iTunes, click "Advanced" in the menu bar, and select "convert selection to mp3". If you skip this step, you will have an VERY BIG uncompressed audio file that you cannot put on the web.

Q3- Why is the WAV file I imported playing back so fast!?

A3- WAV files can come in a variety of different sample rates. A sample rate is the frequency at which the sound was recorded. Most audio programs, including GarageBand, will default to a CD quality sample rate of 44.1 kHz. If a WAV file that was recorded at 22 kHz is imported in and played back at 44.1 kHz, it will play the audio twice as fast. 11 kHz... 4 times as fast... and so on. You must first convert the file to a sample rate of 44.1 kHz. The "quick and dirty" way is to convert to MP3, then import the MP3 (but you are then compressing, uncompressing, and recompressing the file, so you are losing quality). A program like Audacity ( http://audacity.sourceforge.net ) should let you convert the sample rate directly.

Finally, I'll end with some instructions on how to convert your miniDV audio into MP3 in case you are stuck using a miniDV video camera for your audio. First, of course, you record your audio with the camera. :) Since iMovie is installed on all Macs by default, I recommend using iMovie to import the video and convert it to audio. So you launch iMovie and create a new project. Then you plug in your video camera via the firewire cable and turn on the camera. Make sure the camera is in "vcr" or "playback" mode. iMovie will automatically recognize the camera and bring you to the import screen. Rewind your tape to the beginning, and start the import. When you are done, you will have all your clips located in little boxes on the right. Just drag them to the bottom timeline and place them in the order you want. When you are satisfied, click on "file" and "share". Select "Quicktime" at the top, and select Compress movie for "expert settings". Click "share". Under "export", select "sound to aiff". You can then import the aiff audio file it creates into iTunes and convert it to MP3. Simple as pie! Well... kinda. :/

Good luck!
A7