A lot of us never need to get behind the business end of a microphone. But for those who have to present regularly, it is important to have a basic understanding of how different microphones work. Then we are able to adapt our speaking technique to suit the microphone in front of us as we deliver our message. This is a quick guide to using microphones effectively for presenters of all ages!
Microphones are components in virtually all audio systems.
Thus, you’ll hear about studio microphones for recording and PA microphones for live sound. There are boom microphones for broadcast or film shoots. Or instrument microphones which attach directly to guitars or other musical instruments. Then there are boundary microphones or boundary effect microphones for theatre work or conference systems, lapel mics for seminars and business meetings, and headset microphones for telephone call centres. (And this is just to mention a few options). The different types of microphones optimise a range of different requirements in different environments.
That said, all microphones have one thing in common: “microphones convert a sound wave into an electrical signal in which the voltage and current are proportional to the original sound”. To perform this task microphones use a thin membrane, known as a diaphragm, which mimics the function of the human eardrum. Sound waves strike a microphone’s diaphragm and cause the diaphram to move. Harnessing this movement creates an electrical signal.
A sound is essentially a change in pressure that varies in specific ways over time to create specific sounds (sound waves). When sound waves strike a microphone’s diaphragm, they cause it to move, which movement, in turn, creates a variance in an electrical current (aka signal). The electrical signal is transmitted to output devices, which either process the electrical signal (store it, or make it louder, or make it sound like Darth Vader on a bad hair day), or use the signal to recreate sound waves (loudspeakers).
Microphone engineers, over the course of “recorded” history, have developed 3 fundamental techniques for detecting sound waves and “transducing” sound to electrical signals.
A dynamic microphone uses the diaphragm to move a coil of wire within a magnetic field to create the electric signal. It’s advantages are it’s relative simplicity and good voice frequency characteristics. A dynamic microphone is quite sensitive to interference from external electromagnetic fields. If your venue has a hearing aid loop, you don’t want to try dynamic microphones.
A condenser microphone uses the diaphragm to move one side of a capacitor plate thus causing the capacitance to vary. This creates an electric signal. The advantages are it has good resiliency, can cope with large variances in the sound loudness and tends to have a larger frequency response. Condensor microphones are often used for instrument microphones, however, are the basis for many vocal microphones as well. The disadvantage is that the capacitor requires a power source to keep it charged. Therefore, a condenser microphones require either batteries or a power supply delivered from the connected equipment.
Ribbon microphones consist of a thin strip of metallic foil suspended in front of a magnetic plate. Sound waves cause the foil to vibrate, producing fluctuations in the electrical current, creating the audio signal. This extremely sensitive configuration picks up a wide range of frequencies and produces an extraordinarily rich representation of the original sound. The trade-off for this sensitivity is the delicacy of the mechanism – ribbon microphones are very sensitive to physical impacts and power overdrive. (Oh, and very expensive).
The other factor that effects using microphones is the system engineering. A system engineered for voice reinforcement usually uses rather sensitive microphones and try to “hide” the microphones away so they don’t distract from the presenter. A vocal microphone for a rock band vocalist, by contrast, can have much lower sensitivity. In this case, however, the microphone is held within millimetres of the vocalist’s mouth. This means that the microphone “hears” only the voice and not the other instruments around it.
Principles for Presenters
So, as a speaker/presenter, how do you make sure you are heard and understood?
- Learn to recognise – or at least be able to take a good guess – at what internal configuration and pick-up pattern the microphone has. If you have the opportunity to research beforehand, do so. Then adjust your speech style accordingly – speak “firmly” to dynamic microphones, but more relaxed and rounded to condenser microphones.
- When you have a sound operator, work in cooperation with them. A good sound operator will usually have a better understanding of the capabilities of the microphones they can offer.
- While standing normally, move the microphone so you are “looking down the barrel” of the microphone. If you can’t move the mic, move yourself. For guidance in using voice reinforcement systems, a hand-held microphone should be about a handspan from your mouth. Stand-mounted or Lectern mics should be about 15”/400mm away from your mouth. A microphone on a stand will typically be setup for voice reinforcement. Taking the microphone off its stand and useing it as a hand-held will result in excessively loud sound-levels. A good sound operator can help here. However, don’t assume they can read minds, so try to give them some warning what you intend to do.
- Ensure your voice production is clear and controlled. The microphone doesn’t make the sound for you – it reinforces the sound you make. If the sound you make is muddy, mumbled and unclear, so will be the amplified sound.
- Watch your dynamic control. By all means express yourself dramatically – just stay within the bounds of the system capability. If all your drama only bursts your audience’s ear drums, they won’t “hear” anything else. In either sense of the word.
- Watch you don’t move off orientation to the microphone. It’s fine to walk around if you are comfortable with that – so long as the microphone walks with you and stays properly oriented to your mouth. (If you are able, use a wireless microphone such as a lavaliere clipon, developed specifically to address this issue. However, they still need care to setup and use.) Some microphones are more tolerant than others, but just turning your head can make a big difference.
You speak to deliver a message – don’t let the technology become a distraction to that message.