Welcome to the next installment of "Tech Talk." This monthly feature
will hopefully help you understand about certain sound and musical
gadgets that everyone sees but are just not sure how they operate in
the real world.
This month we will be talking about
Microphone Frequency Response.
Frequency Response Charts
A microphone's frequency response pattern is shown using a chart like
the one below and referred to as a frequency response curve. The x-axis
shows frequency in Hertz, the y-axis shows response in decibels. A
higher value means that frequency will be exaggerated; a lower value
means the frequency is attenuated. In this example, frequencies around
5 kHz are boosted while frequencies above 10kHz and below 100Hz are
attenuated. This is a typical response curve for a vocal microphone.
Which Response Curve is Best?
An ideal "flat" frequency response means that the microphone is equally
sensitive to all frequencies. In this case, no frequencies would be
exaggerated or reduced (the chart above would show a flat line),
resulting in a more accurate representation of the original sound. We
therefore say that a flat frequency response produces the purest audio.
In the real world a perfectly flat response is not possible and even the best "flat response" microphones have some deviation.
More importantly, it should be noted that a flat frequency response is
not always the most desirable option. In many cases a tailored
frequency response is more useful. For example, a response pattern
designed to emphasize the frequencies in a human voice would be well
suited to picking up speech in an environment with lots of
low-frequency background noise.
The main thing is to avoid response patterns, which emphasize the wrong
frequencies. For example, a vocal mic is a poor choice for picking up
the low frequencies of a bass drum.
Frequency Response Ranges
You will often see frequency
response quoted as a range between two figures. This is a simple (or
perhaps "simplistic") way to see which frequencies a microphone is
capable of capturing effectively. For example, a microphone, which is
said to have a frequency response of 20 Hz to 20 kHz, can reproduce all
frequencies within this range. Frequencies outside this range will be
reproduced to a much lesser extent or not at all.
This specification makes no mention of the response curve, or how
successfully the various frequencies will be reproduced. Like many
specifications, it should be taken as a guide only.
Condenser vs. Dynamic
Condenser microphones generally have
flatter frequency responses than dynamic. All other things being equal,
this would usually mean that a condenser is more desirable if accurate
sound is a prime consideration.
Foot note: You probably heard the recent announcement
that the upcoming changeover from analog to digital TV broadcasts has
been delayed until June. We've all been inundated (and, honestly, maybe
a little annoyed) by the wave of TV commercials and news stories about
it, but when all is said and done, they have done a good job of
reminding us that the change is coming soon enough.
There's fear and quitea bit of confusion about all of it. I can say
with confidence that none ofyour wireless systems is going to just stop
working on that day, because of the changeover - whew, that's good
news! However, over time you may experience signal interference and
degradation, as the new cell phone services begin to use these
frequencies.
Til next time,
Roger
For custom guitars and basses, check out
Fortner Guitars.
