Digital Sound & Music: Concepts, Applications, & Science, Chapter 1, last updated 6/25/2013
Some microphones may have a very flat frequency response on-axis but due to the
directional characteristics, that frequency response can become very uneven when off-axis. This
is important to keep in mind when choosing a microphone. If the sound you're trying to record is
stationary and you can get the microphone pointed directly at the sound, then a directional
microphone can be very effective at capturing the sound you want without capturing the sounds
you don‟t want. If the sound moves around or if you can‟t get the microphone pointed directly
on-axis with the sound, you may need to use an omnidirectional microphone in order to keep the
frequency response consistent. However, an omnidirectional microphone is very ineffective at
rejecting other sounds in the environment. Of course, that‟s not always a bad thing, as with
measuring and analyzing sounds in a room when you want to make sure you‟re picking up
everything that‟s happening in the environment, and as accurately and transparently as possible.
In that case, an omnidirectional microphone with a flat frequency response is ideal.
Figure 1.20 A small-diaphragm omnidirectional microphone specialized for measurement use
Directional microphones can also vary in their frequency response depending on their
distance away from the source. When a directional microphone is very close to the source, such
as a handheld microphone held right against the singer‟s mouth, the microphone tends to boost
the low frequencies. This is known as the proximity effect. In some cases, this is desirable.
Most radio DJ‟s use the proximity effect as a tool to make their voice sound deeper. Getting the
microphone closer to the source can also greatly improve acoustic gain in a live sound scenario.
However in some situations the extra low frequency from the proximity effect can muddy the
sound and result in lower intelligibility. In that scenario, switching to an omnidirectional
microphone may improve the intelligibility. Unfortunately, that switch can take also away some
of your acoustic gain, negating the benefits of the closer microphone.
If all of the examples in this section illustrate one thing about microphones, it‟s that there
is often no perfect microphone solution, and in most cases you‟re simply choosing which
compromises are more acceptable. You can also start to see why there are so many different
types of microphones available to choose from, and why many sound engineers have closets full
of them to tackle any number of unique situations. When choosing which microphones to get
when you‟re starting out, consider what scenarios you‟ll be dealing with most. Will you be
working on more live gigs, or controlled studio recording? Will you be primarily measuring and
analyzing sound, capturing the sounds of nature and the outdoors, conducting interviews,
producing podcasts, or engineering your band‟s debut album? The answer to these questions
will help you decide which types of microphones are best suited for your needs. Direct Input Devices
Surprisingly, not all recording or performance situations require a separate microphone. In many
cases, modern musical instruments have small microphones or magnetic pickups preinstalled
inside of them. This allows you to plug the instrument directly into an instrument amplifier with
a built-in loudspeaker to produce a louder sound than the instrument itself is capable of
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