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Digital Stories @ UMBC

Audio for podcasts, digital stories, and class projects

Microphone Types

Transducers

There are 3 categories of microphones based on how they translate sound waves into electrical energy: Dynamic, Condenser, and Ribbon Dynamic, the most common and least expensive uses a diaphragm moving against a magnetic coil. These are also the most rugged type microphones. Condensers are more expensive and more sensitive microphones using an electrical charge between 2 plates. They need power from a battery or an external source to work. The external source is usually called phantom power. Ribbon microphones are the most expensive and sensitive. They are usually found in recording studios for recording vocals and soft instruments. They have a thin aluminum ribbon that is suspended in a magnetic field. Your choice should be based on how much you can spend, how rugged the microphone has to be-for example if you are moving it often- and how sensitive it has to be.

 

Pickup Patterns

The next important category of microphones is based on their pickup patterns. This designates which sides of the microphone are designed to pickup sound. The most common is called the cardoid, named after its heart shaped pattern. It mainly picks up sound coming from the front, some from the sides, and virtually none from the back. The near opposite of this pickup pattern is an omnidirectional, which picks up sound from all directions, most importantly the rear of the microphone. For the most part, you'll want to use a cardoid microphone to control the sound you record. However, occasionally you may need an omnidirectional mic to pickup a group of people that may surround the microphone.

 

Shapes and Designs

Microphones come in a wide variety of shapes and designs. In a moment we’ll list some of the most common. Your choice of microphone design should be based on your particular needs in the field or in the studio. Let's look briefly at some of these designs and when you might use them. Hand held or mountable on microphone stand- usually cylinder shaped Boom- usually used in video or film production to gather sound from a distance Boundary or PZM- gathers sound from that bounces off a table or wall Lapel also known as lavalier- for close miking of a singular speaker Wireless- to remove the tether for an active presenter Headset- typically used for webcasts or webconferencing Built-in Microphones- many recorders and computers have them-not usually high quality USB microphones- ouput a digital signal that computers recognize

 

Digital Recorders, Formats, Connectors and Settings

Recorders

Here are at least four initial recorder choices to record your audio

  1. A simple recorder like the Sony UX-80 that sells for less than $100
  2. Moving to a more professional recorder, the Marantz PMD-660 costs around $550 but has many more features and controls than the simple Sony voice recorder.
  3. With a USB mic or a built in mic you could record directly to your computer
  4. And another choice you could use in a pinch is your video camcorder, especially if you can connect an external mic and adjust the levels.

Connectors

Three types of connectors will most commonly use to connect your microphone to the recorder are: XLR- used for low impedance professional microphones Mini-plug 1/8 inch can be found on lower end microphones and recorders-same size as a headphone jack USB- for connecting directly to your computer

Recording Formats

These formats may initially seem like a mixed-up alphabet soup. But we’ll focus on the few you need to know and their attributes. They are recognizable on your computer by their suffixes. Two are uncompressed and produce larger size files. These are wav and aif files. wav (pronounced "wave") is standard digital audio file format for storing waveform data similar to aif wav files but more common on windows based systems. aif or aiff is a CD-quality audio file, similar to a wav file; uncompressed large size files The others are compressed and may be of lower quality than uncompressed files, but they are more portable and can be used for long recording when you don't have enough space on your card or hard drive. mp3 or mpeg 3 are compressed audio file, roughly tenth the size of an uncompressed file such as aif or wav aac is an advanced audio coding file, compressed similar to a mp3 file but higher coding efficiency wma is a windows media sound file a compressed audio file produced by windows media player

Setting Your Sound Levels

Before you start recording there is another decision you need to make. It regards the audio level settings on your recorder. Typically you will have two choices:

  1. Automatic gain, also known as automatic gain control (AGC) or automatic level control (ALC). This setting will put the recorder on autopilot and it will turn up or turn down the sound based on what it senses in the environment. The problem with this setting is, as I will describe later, the audio recorder cannot cognitively judge the value sounds like our brains can.
  2. The second choice is manual gain setting. In this mode you will be setting the desired level based on your hearing (hopefully with headphones) and watching the audio meter. Optimally, you should set the level to move between -20 and -12 db. If you set the level too low you'll wind up with more noise than signal. If you set it too high there will be distortion (sounds fuzzy) or clipping (sounds breaking up).

 

 

 

Examples of Sound Level Settings

Audio Examples

1.

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Level set Too Low- produces insufficient signal to noise ratio

2.

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Good Sound Levels- this is an example of the same audio text with good sound levels.

3.

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Distortion- can be caused by setting level too high, preamp too high, too high on mixer, or mismatch between mic and line levels

4.

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Clipping- can be caused by setting level too high on a digital recorder

5.

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Background Noise- using internal mic and not adjusting for background noises can produce a distracting recording.

Microphone Techniques

These are some tips and tricks that will help you produce a better quality recording

  1. Keep the microphone close to your mouth but not too close
  2. If you have a pop filter, use it to stop the percussive P and hard syllable sounds. If you don't have a pop screen you can make one from a nylon stocking and some wire.
  3. If you don't have a pop screen filter, try to point the microphone at your chin and speak over the top of the microphone
  4. Try to find quiet places to record or help them become quiet by silencing or baffling external sounds.
  5. Be aware of reverb and reflected sounds- there are "live rooms" that have many hard surfaces that will bounce sound back to the microphone at slightly delayed times. You make a room less live or reflective by adding sound absorbing materials. In a studio these might be acoustic panels of fiber or foam. At home you can use rugs or blankets. I should warn you that the converse, making a room too "dead" can sometimes sound unnatural.
  6. Use a mic stand instead of holding the microphone.
  7. Avoid vibrations that might shake the mic stand in the slightest way- you might want to use a shock mount for the microphone.
  8. If you are reading from a script, try to keep it to one page if you can. If it is multiple pages, end each page with the end of a paragraph or sentence. Pause before reading the next page so that you can edit out the page turning later
  9. If you're reading from a script use a music stand or a copy stand like this one.
  10. If you're using a script holder, be aware of sound reflecting off it into your microphone.
  11. If you make a mistake reading your script, pause and go back to the last paragraph or sentence.
  12. Watch your breathing, take your time. Remember that your listeners need time to absorb what your reading.
  13. Try to speak naturally, but don't forget to use emotion and inflection in your voice to convey meaning. Your voice is a gift, use it.
  14. Use headphones to monitor your recording.
  15. Tune your hearing skills to listen to any distracting sounds in your recording environment such as air handlers, squeaky chairs etc.
  16. If you don't have a pzm or boundary mic and want that pickup effect, try placing any microphone you have on to a table so that sound can bounce into it. I've done this when I was stuck with one mic to recording a panel of speakers seated at a table.
  17. Finally, experiment and create your own tools. Find out what works best for you and your situation.