Recording Digital Audio

The following information deals with various ways to record and add audio to multimedia projects, plus additional information about digital audio file formats, microphones and other audio recording devices.

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Information about Microphones

When you are considering what type of microphone to use to record audio narration, the two major choices are the common, and generally inexpensive microphones that plug into a computer's sound card such as the one shown below, and the somewhat more expensive USB microphones that provide better audio quality, discussed in more detail in the next section.

Microphones can play an important role in the use of audio, by allowing you to record your own narration. Different microphones have different characteristics and some of the most important are described below.

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Sound Pick-Up Patterns or Directionality

How a microphone picks up sound is another important quality. The following information about sound pick-up patterns comes from A Primer on Microphones, written by Peter Elsea, and online at: http://arts.ucsc.edu/ems/music/tech_background/TE-20/teces_20.html

• Omni-Directional - The simplest microphone design will pick up all sound, regardless of its point of origin, and is thus known as an omni-directional microphone. They are very easy to use and generally have good to outstanding frequency response. 
   
   
• Bi-Directional - It is not very difficult to produce a pickup pattern that accepts sound striking the front or rear of the diaphragm, but does not respond to sound from the sides. This is the way any diaphragm will behave if sound can strike the front and back equally. The rejection of undesired sound is the best achievable with any design, but the fact that the microphone accepts sound from both ends makes it difficult to use in many situations. Most often it is placed above an instrument. Frequency response is just as good as an omni, at least for sounds that are not too close to the microphone.
   
   
• Cardioid - Named for the heart-shaped pick-up pattern, this pattern is popular for sound reinforcement or recording concerts where audience noise is a possible problem. The concept is great, a microphone that picks up sounds it is pointed at. The reality is different. The first problem is that sounds from the back are not completely rejected, but merely reduced about 10-30 dB. This can surprise careless users. The second problem, and a severe one, is that the actual shape of the pickup pattern varies with frequency. Variations of the cardioid microphone include a super-cardioid microphone, which has a tighter pickup pattern than a regular cardioid microphone--it doesn't "hear" as much sound from the sides; and a hyper-cardioid microphone, a  very specialized microphone. A good example is a shot-gun microphone. The microphone "hears" only what it is pointing at--nothing from the sides and very little from the back. 

                

 

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Styles of Microphones

There are many different styles of microphones and they come in many shapes and sizes.

• Handheld microphones are (as the name suggests) held in a person's hand or may be placed in a microphone stand.
   
    
• Lavalier microphones are usually clipped on a speaker's clothing, such as their tie or lapel. These microphones may be wired or, more popularly, wireless. Hanging microphones are usually suspended by their own cables and may sometimes be found in orchestras or choirs. 
  
  
  
   
• Shotgun microphones are often mounted on poles and pointed toward the speaker(s). These microphones may often be found when movies and television shows are being made.
  
  
   
• Computer microphones are becoming more popular and many computers and digital devices now include built-in microphones.
  
  
   

IMPORTANT NOTE:
The sound quality of your recorded audio is fair when using this type of microphone, however, the quality of your computer's sound card will also contribute to the quality of the recording at least as much as the quality of the microphone you are using.

The cable at left has a metal tip called a mini-plug on one end. The other end is wired directly into the base of the microphone. The plug end is called the male end, and is one eighth inch in diameter, so sometimes you may hear this type of connector called a 1/8th inch connector. This type of cable is often used for audio and is frequently found on headphones used with portable audio players. A single stripe seen near the end of the metal plug indicates that this is a monaural cable, while two stripes indicates that this cable supports stereo sound.

 

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USB Microphones

Another popular computer microphone does not plug into the computer's sound card, but instead uses a USB connection. The picture at left is a Logitech USB Desktop Microphone that usually sells for between $20 and $25. This microphone should provide good quality regardless of the type of sound card your computer has since it bypasses the sound card. It does not require any additional software or drivers and should work well on any computer that has a USB connection.

More expensive USB microphones, such as the ones shown below, offer significantly better sound quality than the less expensive models.

	Samson C01U Microphone $79 http://www.amazon.com/Samson-CO1U-USB-Condenser-Mic/dp/B000AP1RE8/ref=sr_1_1?ie=UTF8&s=musical-instruments&qid=1222788296&sr=1-1
	Audio Technica AT2020 $116 http://www.amazon.com/Audio-Technica-AT2020USB-Condenser-Microphone/dp/B001AS6OYC/ref=pd_cp_MI_3?pf_rd_p=437171301&pf_rd_s=center-41&pf_rd_t=201&pf_rd_i=B000EOPQ7E&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=12QS3NRFGAREDXG44PAR
	Rode Podcaster $229 http://www.amazon.com/Rode-Microphones-Podcaster-USB-Microphone/dp/B000JM46FY

 

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USB Microphone Settings on a PC

When you first plug a USB microphone into a PC, you may need to change some audio settings to make sure the computer recognizes the microphone. In the Windows XP operating system, you should first go to the Start menu and click on Control Panel.

 

Next click on the Sounds and Audio Devices icon (as shown below left), or if you are in the Category view (as shown below right), click on the Sounds, Speech and Audio Devices link.

        

This will bring up the Sounds and Audio Devices Properties box. Click on the Audio tab.


 

Use the pull-down menu under the Sound Recording in the middle of the box and the name of your USB microphone should appear in the list. Make sure it is selected and then click Apply and OK.

 

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Tips on Recording Audio

• Perhaps the biggest tip on improving audio recording is this: get the microphone close to the mouth when you are recording yourself or someone else speaking. However, this can also cause a problem by emphasizing the sibilant sounds, sometimes called "plosives." Plosives occur when a microphone is too close and you get the popping sound when using words with the letters "P," "B," "T," or "S." Higher qulaity microphones can help and you can also try placing a windscreen over the microphone to reduce plosives. (Hint: a clean stocking or a sock can make a good low-budget windscreen.) Or if your microphone is too small, or you don't want to sacrifice any footware, you might try moving the microphone to the side of your mouth so that you are not speaking directly into the front of the microphone. This technique can really help but you may need to speak louder or increase your recording volume to compensate for moving away from the main pick-up area of the mic.
    
• Try to record narration in as quiet a setting as possible. Relax and read slowly, annunciate each phrase.
   
• Do several takes. Don't be discouraged if you mess up a lot, even professionally trained narrators make mistakes and require many takes.

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WS-100 User Manual
http://www.olympusamerica.com/files/WS100200Sman.pdf

Frequently Asked Questions for WS-100
http://www.olympusamerica.com/cpg_section/cpg_support_faqs.asp?id=1170
 

 

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Marantz PMD 660 Digital Recorder
Lists for $650; but is available for $499

front view	rear view

The PMD660 is a hand-held professional digital audio recorder that has two built-in microphones or accepts professional quality XLR microphones. Records to Compact Flash (CF) memory cards in both WAV and .

More info:
http://www.transom.org/tools/recording_interviewing/200503.pmd660.html
 

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Digital Audio File Formats

Like graphics, audio can be stored on a computer in several different file formats. For a long time, the computer industry standardized on one audio file format for the Windows operating system: .WAV - the Windows Waveform audio format for the PC. The Waveform audio format offers high quality sound but the file sizes can be very large. Wav files store a representation of the actual sound wave being recorded so if your computer has speakers attached, they tend to sound good and the sound is generally the same computer on which they are played.

Characteristics of Waveform Audio Files

Generally speaking, there are two main characteristics of waveform files that one needs to worry about when recording: stereo and sampling rate. Essentially, setting these at their optimum level will result if very accurate sound recording but very large file sizes. The trick is the match the levels with the quality you need.

Stereo is the easiest one to grasp. If you record in stereo, your file size typically doubles as the machine must record two channels instead of one. For courseware and presentation multimedia it is rarely necessary to record in stereo as the aesthetic quality gained by stereo recording typically does not outweigh the smaller file size gained by monaural recording. Indeed, if you are presenting from a computer, the stereo effect will usually be lost on your audience due to the characteristics of the room and speaker placement. Also, it is usually silly to record your voice in stereo as both channels with be nearly identical.

Other Audio File Formats

Nowadays on the web with the emergence and diffusion of new audio technologies and the widespread use of cross-platform streaming audio technology, there are even more choices. In addition to .WAV files, some of the other common audio file formats found today are:

.WMA (Windows Media Audio)
Microsoft's Windows Media file format for audio. This format is gradually replacing the .wav format because it uses new technology to dramatically compress the file size of an audio clip, yet still retaining very good sound quality.

.MP3 (MPEG-1 Audio Layer-3)
So much has been written about the MP3 format and how it has been used by millions of people around the world to illegally download and share music files; yet MP3 is a legitimate (and legal) audio file format that has gained popularity over the last several years. The major advantages of this format is that it is cross-platform capable (which means that MP3 files can be played on Windows and Macintosh computers), and like the WMA format, its compression scheme greatly reduces file size without sacrificing too much audio quality.

Real Audio
Real Audio is one of several "streaming media" formats that have been developed specifically for the web. These files require a web browser plug-in, a free program that allows audio to be played from links within a browser such as Internet Explorer. Audio files such as those from Real Audio are streamed to your computer, which means they can be played as they are being downloaded, rather than having to wait until the entire file is downloaded, a process that can take a long time when large audio files are involved.

AAC (Advanced Audio Coding)
This audio format is supported by iTunes, the popular online music store run by Apple Computer.