Hi everyone, I'm Dennis Foley from Acoustic Fields. Today we're going to talk about room
frequency response. A lot of enquiries
from customers about
the room that they have, it has this size they have the sources, sound sources in
the room.
They have these low frequency drivers with these diameters.
A lot of them don't go through the
next step and measure the room response but
you know obviously we can predict a little bit with dimensions and
sound sources and things like that,
but some do have measurements
and this is an issue I see all the time that's confusing
for them. So let's talk a little bit about it. Let's say you run a
room frequency response and what is that? Well that's the signature of the room,
that's how the room reacts to
sound energy that's put with in it. That's its signature just like when you
sign
your name to a document, to a cheque, a contract or anything like that,
that's your signature authorizing it. Well this is the room authorizing the sound
that's in it.
And this is a picture of how it's authorizing in that manner
okay? And usually it's not smooth because today's rooms are very small so there's
a lot of issues that we have to address.
A common graph that I see
in rooms that are measured our peaks
and troughs so we have high points and low points.
If we take this as our baseline in our center measurement we have
energy signatures above the line
and we have energy signatures below the line. Now
what do those two energy signatures have in common? What does
a peak of plus 10 DB
and a dip of minus 10 DB have in common?
What do both of these areas have in common? Well the one thing they have in
common
is pressure. These
signatures are both reactions,
the rooms reactions, to certain frequencies,
say here and here,
the room reaction to 500 and 200 cycles.
So it really doesn't like 200 and it really doesn't like 500. Now what way
does it not like those?
Since they're both pressure related, one is an exaggeration,
one is an attenuation, or lack of energy.
You can't EQ your way out of these. You can't dump
500 cycle energy into this pressure area and bring it back to normal, not of its
-10, -15 DB you can't do it. You could
blow your EQ up trying, but the room simply won't let you
so both of these peaks and troughs are reactions to pressure.
You squeeze your lips together and then blowout and your cheeks expand
that's how your room is reacting to pressure. That's how the room is reacting
to 200 cycles in our example here.
So it's all about pressure. So how do we manage that pressure?
Well that's where different sound absorption technologies come in.
So if this is a common situation that we see,
what's a good graph to look at?
Well we want something like this.
We want something plus two
or minus two over our baseline.
Not easy to achieve but not difficult.
Most your professional recording studios, most of your top engineering design
firms
use this is a a guideline. So it's a good marker.
You can see in our top examples, and this is typical of some of the room responses
that we receive,
big, big difference. This is
minimal room sound. This is lots of room sound.
Thank you.