Okay. So, we've been talking about Helmholtz
resonators and bottles. And you're probably wondering now, what
in the world are we talking about bottles for if we're talking about audio and
music engineering. And in particular if we're interested
maybe in the design of speakers or cabinets for guitar amplifiers for
example, as we had discussed earlier. Well, it's pretty simple, and it's, it's
pretty significant. we're interested in the resonant
frequency of bottles. because for a closed speaker cabinet
design in particular, the stiffness of the cabinet is defined by the density rho
c squared speed of sound in air squared, the area, surface area associated with
the driver itself, okay. And so, if I put a speaker, a loudspeaker
driver in a box here. this is going to have a certain radius a,
okay. And then I can compute that surface area
as pi a squared there, and I end up with a stiffness in the box that's defined by
that surface area and the volume of the box itself.
Okay, so this basically ends up looking a whole lot like our discussion earlier on
the Helmholtz resonator. And that's why it's significant, because
we can now compute the stiffness of the cabinet as the function of the density,
the speed of sound squared, the volume of the box itself.
And the radius of the driver, the speaker component that you put in the box.
And this is, this part's important, because if you notice the, picking a
fixed volume for a box. So, keeping this fixed doesn't mean that
you have a fixed stiffness here, because it depends upon how large the driver is
that you choose to put in the box, and we can see that here.
and it varies significantly as a result of that because it's the area squared.
so changes in the radius can significantly affect the stiffness of the
speaker. Okay, I think that's enough with respect
to the intro on the on, on the, on the domain at resonance and how we hear.
And we will be working in our next lecture I think to talk a little more
about electronics and fundamentals of electronics.
And the next time I have a chance to speak with you we're going to talk a
little bit more about resonances in particular, and start relating that to
room acoustics.