Hi everyone, Dennis Foley from Acoustic Fields.
Today we're going to talk about noise and play black levels in your room.
there's a ratio here that that I found through the years that works really well for music
and playback and we're going to talk a little bit about how that all works.
So room noise levels obviously are expressed in DB and we know that DB is the unit of measure
and SPL is the container in which that measurement is placed so to speak, a pressure level so
it gives us a reference point.
Now how do we find that out?
well there's an app, it's really easy to use on your iPhone, it's called DB meter and you
can see the icon and download it, I think it's a couple dollars.
It gives you maximum pressure, it gives you minimum pressure, it gives you average, gives
you real-time readings and I use this a lot in rooms and the iPhone is becoming…
well it’s a computer I guess so it has speed and storage and you can do a lot of things
with the application.
Most of them are accurate; they're accurate enough for readings like this.
I found the microphone on the iPhone is within one or two percent of real accuracy compared
to our lab test instruments that are right on so it's pretty good if you can get a device
that's portable pretty reasonably priced and can get you within one or two percent that's
pretty good.
So what have we found in our rooms?
so if you take your iPhone and you download the DB meter, decibel meter app I think it's
called and do some measurements in your room and do it over a few days, do it over you
know different times during the day you'll find that in most rooms this is what we find,
we find it 50 DB SPL is on average no music playing in the room, just ambient background
noise from traffic etc. and stuff that 50 is a good average in your room today.
40 is really quiet, the difference between 10 DB in ambient background levels in a room
is huge and I really don't have the words of the vocabulary to describe that difference
I know it only looks like this on paper but it's huge to your ears and then the next level
here is the 30 dB.
You're not going to get that quiet level of quietness without a structure over your existing
structure so without the proper barrier and vibrational isolation stuff.
I built a room in Tucson that has a 25 dB noise level, now what do we have to go through
to get that?
Two rooms, two separate foundations, 8 inch poured concrete each with 20-foot high walls
and eight inches of air space between the two wall and we were able to do that if we
located it out in the countryside.
Our biggest problem at that point was vibrations from the earth so the building and the foundation
were separated and put on Isometric Springs so you can get this.
Now at this quietness you can sit in the chair and hear your heart, that's really quiet so
this will give you an idea of the ratios that we work with.
So this is average (50 dB), this is good (40 dB) and this is excellent (30 dB).
So what do we do when we play back music in this?
We always have to elevate the music and the playback levels above the noise that we're
facing in our background so the less noise we have in our room the lower we can play
our music and the lower you play your music and the less energy you put in the room more
detail, presence and quality of sources is heard because energy can be confusing to our
ears, our ears are small really and not designed to handle a lot of energy so the less energy
we put in our rooms the more we're going to hear and if we hear more we're going to connect
more emotionally to the music.
Stereo Phile, a popular high pride magazine did a survey many many years ago and one of
the things that caught my eye was that people actually measured the pressure levels that
they listen to, 83 was the average so if we take that 83 SPL and we put it over our nose
levels that we have in our room, let's take the good (40 dB), you can see it's about 2
to 1 ok so that's a good kind of rule of thumb to go by, if you're 90 dB, if you're doing
really loud stuff you know then your background should be 45 so there's about a 2 to 1 ratio
there.
The lower the noise floor in your room, the more music you're going to hear and it's subtle
and every DB that you get below 50 is a huge and dramatic impact.
Now it has a huge cost, the cost between this (50 dB) and this (30 dB) is lots of money
because now we're getting into the realm of isolation where we have to isolate from the
earth, we have to isolate from airborne energy, noise transmitted through structures so it's
really really complicated.
I was in an anechoic chamber one time in New York that had a noise floor of 21dB, you can
imagine how quiet that was and no reflection so it's really discerning.
Some people sitting there and they get sick because you know as humans we need reflections
and distance for localization to keep kind of a homeostasis of balance if you will but
didn't bother me, I was very interested in it.
I sat there I think for an hour, they had to throw me out but it was really interesting
to hear something that quiet as I had come close to it but never that that quiet.
So you want to change this ratio in your music room in your favor obviously within your budget,
you have to do that so if you have a 60 to a 70 DB noise level in your room you're going
to have to reduce that in order to hear music.
So I hope this helps, roam ambient, noise levels, playback levels, balance, ratios got
to keep all of it mind.
Remember, just like amplifiers, the first 25 watts of your amplifier is always going
to be the best sound.
The lower you get your noise levels in your room the less energy you have to put in the
room to
hear
more music.
Thank you.