MAS- transmission question

[colterphoto1]

Hi Mark,

A Klipsch fan writes in that they are experiencing problems with noise transmission to a neighbor. I can take the efficiency of their speaker and determine the theoretical max SPL at 1 mtr using the peak power handling as the point of 'destruction' of the loudspeaker.

Can you help with how to use the transmission characteristics of standard home construction (walls, windows) STC as well as the reduction of db through exterior air?

The goal is to calculate the max SPL the loudspeaker could present to a person X feet away from the speaker through the building walls and a moderate distance.

Thanks,

Michael

[DrWho]

I was just thinking that it'd probably be easier to just measure the maxSPL of the system at X feet away []

[mas]

[:|][]

Mike, each wall construction variable, be it material compositional or topological (design) will vary. And then any variations due to flanking vectors such as windows, doorways, air ducts, etc., etc., would act as wild cards that would radically alter the best wall transmission calculations.

Deriving a formula for each combination and permutation of design factors and topologies would be a bit of a challenge.

Gain loss through air, ignoring humidity and temperature, is simply inversely proportional. For each doubling of distance, the intensity will be 1/2.

And I suspect that we would end up with a program akin to the room mode calculators whose model assumptions deviate significantly from the real world circumstances to render them into fancy computer audio games...they give you a guestimate, but not one I would place much money on.

The actual practical solution would be as Doc suggests... to simply cut to the chase and measure the amount of sound transmission for a given signal. This is very easily done with an SPL meter, or in a more troublesome manner for time variant dynamic environments for the sake of argument, with Noise Level Analysis software which will analyze the noise levels over a period of time. (Troublesome because you usually have to sit with the gear for the time as expecting an expensive piece of gear and a computer to remain in the same spot and to not grow legs is a real concern in that type of measurement!).

If the desire was to develop a predictive model prior to building, I would simply specify the most efficient and economical model using double wall construction. (if you need this, please let me know).

[boom3]

It's simple to answer this question. Find out what volume, at what hour of the day, (very important) is acceptable to your neighbor. Take note of where your volume control is at that level. That's it. That's how I settled a couple of noise problems in multi-family situations I've lived in.

If the problem persists, try moving the speakers away from common walls and using a thick isolation pad to decouple the bass, as much as is possible, from the floor. I know this is anathema to to most of us, but it may just pacify the neighbors.

[colterphoto1]

Thanks guys, but from the letter, the damage has been done. It sounds like they're in court.

What's the quick formula for the max db of a speaker?

Doc got me the -6 db/half distance in free air equation

I'm leaving the building entirely out of it, the STC is at mid frequencies only anyway.

It looks pretty close. I'm getting 86 db at 120 feet, they're trying to prove that it could not possibly be over 90.

[DrWho]

Isn't it the burden of the "complainer" to prove that the levels were too loud? If they don't have an SPL meter to prove it, then I can't see how it'll hold up in court? Or at least it shouldn't hold up.

But I think I see where you're coming from....they want to determine the maxSPL of the speakers to show that at the distance the speakers are that it couldn't possibly be too loud. What's the max SPL of the speakers in question? 120dB ish? 120ft is about 36m and at 32m you've already got 30dB of attenuation from distance, which is going to put you right at 90dB (if you can really crank 120dB outta the speakers). And that's not even accounting for any losses through walls and all that (which can be anywhere from 10dB to 60dB depending on the construction).

I did a quick search and you might find this SPL calculator helpful:

http://www.doctorproaudio.com/doctor/calculadores_en.htm

[Guest " "]

"It looks pretty close. I'm getting 86 db at 120 feet, they're trying to prove that it could not possibly be over 90."

I can see avoiding complications by excluding room dynamics....but you can't ignor equipment capabilities....can his amp even drive the speakers to those levels?

Here's the max SPL calculator.  It will factor available amplifier power, sensitivity of the speakers, and distance to get you the answer you want.   No BS.

http://www.myhometheater.homestead.com/splcalculator.html

[mas]

Most munipalities have noise standards developed in the Cambrian Age, with rigorous level verification standards(sic) to match. (e.g.: Can it be heard at a distance of 50 cubits?)

Most become a pissing contest with the arbiter being the subjective opinion of the poor law enforcment officer who responds to the call - and heaven help us if the music played is not to his or her liking. Speaking from a strictly personal POV, the poor bastard would be screwed if i could even faintly hear rap music!

Many laws are based upon subjective standards, and few officials are equipped with sound level measurement gear. Hence the few calls tha i receive to see if I will trot my stuff out and sit all night running NLA measurements trying to avoid moisture and bugs from doing damage to the equipment.

If you are to prove your case, a calculation is worthless as it is fundamentally speculative.

Evidence that can be entered (to the chagrin and 'confusement' of all in attendance) will be a verified maximum SPL measurement taken at the scene with the equipment being played at a verified maximum level, And then let the entertainment begin as you try to explain the concept of a dB to the court. Have fun.

(Ironically I offered to verify such a situation in Dunedin, Florida last fall, only to receive a bemused response of 'why do we need that measurement stuff when a person can hear it?' with regards to an objective SPL level....All I can say is that such cases reinforce Twain's observation that "God somewhat overestimated his abilities when he created man". And we fancy ourselves to be the most intelligent lifeform in the universe. That seems to me to be a pretty good argument for the opposition who maintains a position against the existence of intelligent life in the universe...)

[Guest " "]

"if you are to prove your case, a calculation is worthless as it is fundamentally speculative."

That's fine...but the questions was to provide the calculations.

We don't know if the plaintiff's  are using a calculation of some type or measured responses.

Maybe the best thing to do is to do a calculation, then a measured response....if there is a gap...argue that the plantiffs calculations are , as you would say, worhtless.

[mas]

Given that we do not have sufficient details to complete a calculation even if we wanted to do so, I guess you could still sit there trying to calculate it.

"Now, if we just insert a transformer here, and place the other transformer there...."

Be my guest. BTW, the request was not for a free air calculation as the link provides. There is the tiny issue of a wall...Nor does that "calculator ... account for room acoustics, amplifier dynamic headroom or off axis listening positions".

Simple point source intensity levels are given by I= (Pav/4pi^3). But we know neither the Q, nor room loading, nor wall characteristics. Heck, even a lawyer who hated math and physics could easily rip any such calculation a new one and destroy your credibility. And all that is required is to introduce doubt, one does not have to disprove it.

And " We don't know if the plaintiff's are using a calculation of some type or measured responses." What!?!?! So the neighbors have conceivably calculated the potential for disruption or damage?!

If someone were to write a book proposing the wacko directions these threads take no one would believe it.

[DrWho]

If someone were to write a book proposing the wacko directions these threads take no one would believe it.

But that's why they're so much fun []

Btw, if a lawyer tried to destroy your credibility for using a point source calculation, an even better lawyer would return with the fact that introducing more variables (like narrower Q and walls and all that) will only result in a lower value for the calculated maxSPL. So if we're already home free with the point source, things are only getting better.

[mas]

If someone were to write a book proposing the wacko directions these threads take no one would believe it.

But that's why they're so much fun []

Btw, if a lawyer tried to destroy your credibility for using a point source calculation, an even better lawyer would return with the fact that introducing more variables (like narrower Q and walls and all that) will only result in a lower value for the calculated maxSPL. So if we're already home free with the point source, things are only getting better.

I hope that you are the lawyer who debates against me, grasshoopa!

Narrower/higher Q reduces the amount of steradians a given amount of energy is directed into, increasing the SPL!!!! Just like the focused beam of a Maglite flashlight is brighter than the unfocused flood setting at a given spot. So a speaker suspended in the air is louder than with corner placement????? And a window in the wall can almost negate the presence of the wall as a sink.

Versus the measurement or experience of a reporting officer, the calculation will normally lose - especially if the noise ordinance.does not dictate a specific decibel level - and most do not. Most laws are not based on specific objective dB measurements for the simple reason that few law enforcement departments have dedicated printable SPL meters. In fact, the San Antonio counscil just proposed buying printable SPL meters at over $4K apiece!!!!! (I was appalled at the price!) And don't mention RS SPL meters...

Bottomline: A calculation is speculation that is fraught with assumptions that can be challenged. And all you have ti do is introduce an element of doubt, as you cannot even get up there and testify that your calculation is irrefutably reliable! Doubt is equivalent to disproof. An empirical measurement holds up unless gross negligence can be established.

And the next time you get a speeding ticket, impress the judge with your calculation showing you were not speeding and compare it with the officer's statement that he clocked you on radar. You can buy the beer with the money you save! [] ...not![]

[Coytee]

And the next time you get a speeding ticket, impress the judge with your calculation showing you were not speeding and compare it with the officer's statement that he clocked you on radar. You can buy the beer with the money you save! [] ...not![]

I hear it's possible to beat the rap, even in small rural redneck speedtrap Tennessee towns... something to do with having connections...??

[:^)]

[DrWho]

If someone were

to write a book proposing the wacko directions these threads take no

one would believe it.

But that's why they're so much fun []

Btw, if a lawyer

tried to destroy your credibility for using a point source calculation,

an even better lawyer would return with the fact that introducing more

variables (like narrower Q and walls and all that) will only result in

a lower value for the calculated maxSPL. So if we're already home free with the point source, things are only getting better.

I hope that you are the lawyer who debates against me, grasshoopa!

Narrower/higher Q reduces the amount of sphereradians a given amount of energy is directed into, increasing

the SPL!!!! So a speaker suspended in the air is louder than with

corner placement????? And a window in the wall can almost negate the

presence of the wall as a sink.

I knew you were going to bring up the Q, but the problem with that

is the sensitivity and maxSPL for the speaker are calculated at the

peak of the Q. Assuming a point source assumes more output where the

actual Q dictates that there is less output.

Btw, every apartment and city I've lived in has the noise ordinances

specified with actual SPL levels. For instance, Urbana is 85dB

A-Weighted until 10:30pm when it drops to 70dB (or is it 65dB? I forget).

[mas]

And the next time you get a speeding ticket, impress the judge with your calculation showing you were not speeding and compare it with the officer's statement that he clocked you on radar. You can buy the beer with the money you save! [] ...not![]

I hear it's possible to beat the rap, even in small rural redneck speedtrap Tennessee towns... something to do with having connections...??

[:^)]

OK......so in that isolated case I guess my devious 'calculations' did win out, although I doubt they would have appreciated any math! 'Go Vols!' []

And doc, since we are simply beating this issue to death, Q is not a portion of a point source's output!

In a point source, all energy is eminating in equal intensity in all directions equally. In speaker Q we are consolidating the total energy into a subset of the total 3space field.

Hence, in a corner placement, with Q=8, we are consolidating the available energy into 1/8 of the total 3space volume, rendering the commensurate increase in gain due to the effective power having been doubled 3 times.

Here is a picture. (Wheeeee!) ...Sorry it is not in color for you. [][][]

And many municipalities do not have noise limits in terms of objective dB SPLs. If only....then they could be challenged. Rather they are in terms of audibility at a given distance.

[colterphoto1]

jeepers guys, it was just a fun interesting handwritten letter request from a Klipsch fan and I was trying to help them and have some fun with it. I haven't a clue about the legal issues or what they do with the calculation, but we can come up with the best expert advice possible can't we?

Doc, I used no STC because there so many variables in construction, the chance that the windows leak the most is a very real possibility so wall construction does not matter, and STC is rated for mid band only (as you pointed out). There's no way of calculating how much low end the house absorbs without an actual measurement.

I am leaning towards the conservative sound reduction in all cases so the number is reasonable from all perspectives.

They did ask "is there anything that can be done except to move to a cave in the middle of Utah?", which I thought was particularly witty.

[Guest " "]

" but we can come up with the best expert advice possible can't we?"

the concept of teamwork is new to a lot of folks...working together for a common goal........need to start with something simple....like writing a brief narrative on how to unwrap a piece of juicy fruit gum......yeah I know....it still would be a 50 page thread with hundreds of thousands of different paragraphs on all the issues that could complicate unwrapping the piece of gum...best bet would be just to swallow it with the wrapper.

[mas]

...or I am sure that there is some way that we could simply employ a transformer.

[colterphoto1]

I saw Trey manufacture a BNC adapter with a paper clip and a ding-dong wrapper once.

[DrWho]

lol Colter, Mark and I were just having fun (this is what nerdy no-lifes do in their free time) [8-|]

I'm sure somewhere in here you've found an answer to your questions???