Something to try this weekend with your R/S sound meter

[Don Ferrette]

Now before I go any further I am going to say that this post is for information & for those of you who have or have access to a Radio shack dB meter to try this for yourselves only. It is not up for debate, dispute, basis for argueing the rule or anything of that nature so please don't even think of posting anything like that here. Anyone who does so I will request the powers that be to have said post removed as we need to stop this insane bickering & move forward, this is an attempt to do just that. With that being said on to the good stuff.

Follow along on some really good info from our dB calibration connection at an area Air Force base & what we need to do that can have a significant impact on our attempts to measure dB's with the Radio Shack meter. This individual, because of the nature of what he does, needs to remain nameless but he has been a sound expert with the Air Force for over 17 years-

There are 2 different types of microphone pick ups (mics) used in dB meters, omnidirectional & unidirectional and the Radio Shack is omnidirectional from what this guy told us. We now have, on loan from the Bayer Corp., a $2,000 dB meter that he just completed calibration testing (it was basically on the money) that is fully ANSI S1.4-1983 compliant which is the standard recommended for outdoor sound measuring of automotive or internal combustion engines, pretty much things like race tracks & arenas which happens to be similar to what we are trying to do. This meter has a unidirectional mic in it that is distinguished by it's longer pickup inlet. The unidirectional is more target specific or one as in "uni" and less hampered by reflective noise. The Radio Shack meter uses an omnidirectional (multidirectional) pickup because it's primary selling point is for home stereo use where you do want to take into account the reflected sounds. For those that remember them think back to when the first Bose 901 home stereo speakers came out, they were totally based on reflected sound. Anyway regardless of that the R/S unit still is a fairly good meter & the +/- 2dB in the specs is really rather excessive based on what our guy has told us. The calibrated R/S meter & the ANSI meter in some quick tests were within about a tenth of each other in the 80-100dB target range (and just a note the R/S meter when it got calibrated was barely off in the 80-100dB range). The thing that is killing the R/S meter readings is the reflected sound. Now here's the good part, all one needs to do the make the R/S unit much more of a unidirectional type pick up is to push roughly a 2" piece of the 90 size (approx. 7/8" i.d.) silicone pipe coupler up over the inlet ( you want about an 1 1/2" remaining in front if inlet) so the mic or pickup now has to focus through the tube. (the 1 1/2" distance is about where the mic is placed in the inlet tube of the unidirectional meters, the R/S mic is right at the front) Based on the info from our Air Force buddy this should have a major impact on the R/S meter being much more directional & better suited for what we are trying to do. While I do not own a Radio Shack meter this has already been tried for me by someone who does own one & the difference was quite distinct. He was not however able to do this with boats because of the cold weather in his area, he had to experiment with outdoor yard equipment to generate a sound test bed. I'm hoping some of you who can run this weekend and has or has access to one of these R/S meters to add on the silicone tube & give this a try and see for yourselves. This could be a very big step, but certainly not the only one, in getting things better for this season. Good testing to all. B)

 

[Ray Sametz]

Don, You want numbers with and without the 2" silicone coupler. Ray

 

[Don Ferrette]

Don, You want numbers with and without the 2" silicone coupler. Ray

Ray I'd like for folks to see not just maximums but when you start & stop picking up the boats & the ability to focus or target the area you want to measure. B)

 

[John Knight]

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

 

[Brad Christy]

John,

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

Quite the contrary. Wind activity (direction, speed, etc...) is one of the major unpredictable factors that is currently hindering the effective enforcement of the noise rule. Where the reflective qualities are somewhat predictable, meaning once you know what a given ponds surroundings are going to do to your SPL readings, they can be taken into account (somewhat) at a sanctioned event. Wind effect, on the other hand, is totally unaccountable, and (IMHO) is probably going to be the downfall of the noise rule as it stands today. While I agree that we need to do what we can to quiet our boats as much as possible, I will strongly disagree with any punishment for an infraction of the rule until we can reliably assess the infraction. If we can get some accountable data using the unidirectional SPL meter (even if it is a modified omnidirectional one), specifically in regards to wind effects, I think this will prove invaluable in our efforts to resolve this noise rule issue. Our club has an SPL meter (I think it's the same R/S unit Don is referring to), and as soon as the water clears up and the weather breaks, we will be out there gathering data ourselves and we will contribute our findings in a timely manner.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

 

[Watercadet]

Don, Love ya man, I just have to wonder why we care about a uni-directional sound as apposed to an onmi-directional sound.

From what I understand the noise rule is there to keep people from getting annoyed with our boats and to protect our own hearing. That understood, what does it matter what sound the boat makes 1) by itself 2) in a straight line from the meter and 3) in a certain direction? I would think that the "real world" db measurements would need to be taken as a human ear would function-in an omni-directional pick up, which would include a type of din that the uni-directional mic would not account for.

 

[Ron Olson]

This is going to be good reading. I've got the R/S digital dB meter and I should have some silicone coupling that I'll have to try out on it.

So far this has been the only economical way for most of us to get an idea of how much noise we are making.

I went to a Flint record trial and although I didn't have anything to run, I did have my R/S dB meter in the truck. I stood next ot the high-dollar meter that they had there and got the very same readings as what theirs did.

Racers don't want to drive to a race to find out that their boats aren't legal so we do need a way to make sure that they're in the ballpark. Even with figuring in the tolerance of 2 dB +/- they'll know if there is more work to be done. It sure doesn't hurt to be well under the 92 dB limit either. My boats are at around 87 dB.

 

[Don Ferrette]

Don, Love ya man, I just have to wonder why we care about a uni-directional sound as apposed to an onmi-directional sound.From what I understand the noise rule is there to keep people from getting annoyed with our boats and to protect our own hearing. That understood, what does it matter what sound the boat makes 1) by itself 2) in a straight line from the meter and 3) in a certain direction? I would think that the "real world" db measurements would need to be taken as a human ear would function-in an omni-directional pick up, which would include a type of din that the uni-directional mic would not account for.

Well Adam you're right, it is all about quieting the boats down & I wish it was that easy. However, since one of the main arguements was that you can't measure sound accurately outdoors, we needed some factual information & that came in the form of the ANSI S1.4-1983 standard. This is the standard now in place for race tracks, drag strips & such that are implementing sound level limits and with them being surrounded by lots of concrete & steel I can't think of a venue more affected by reflected sound. The meter from the Bayer Corp. is fully ANSI compliant & is unidirectional so that's the benchmark we need to use. The cool thing is that, so far, the mega buck ANSI meter & the calibrated R/S meter with the silicone extension have read the same in initial side by side testing. Is this alot of extra work, you bet but I want to have the technical data & real world results, not a bunch of he said, she said stuff. And for the record this is not the only thing "in process" on this rule, more will follow.

And BTW- for those who can test this out this weekend I also ask that you set the meter on a one or two inch thick piece of soft foam on a stable platform to measure as opposed to a tripod and have the pickup end out past the edge of the foam. One thing that has come up is that an improperly counterbalanced and/or being too rigidly mounted on the tripod can actually increase your readings. A piece of soft foam is cheap & simple way to eliminate that variable. B)

 

[Grimracer]

Brad,

I did not get your post? Contrary?

Grim

 

[Terry Keeley]

Hey Don:

Where are we on the calibrating of meters? I think Randall Thomas had a calibration unit he was trying to fix for us, wasn't he?

Do the meters "drift" that much? Is there an easier way to check them?

ps: Sounds like some constructive work, thanks!

 

[bzubee]

That was an instrument John Equi purchased on his own and it needed calibration which I'm having done at our Calibration lab once that is done we can easily keep our meter within tolerances. John got the unit from E Bay.

Hey Don:
Where are we on the calibrating of meters? I think Randall Thomas had a calibration unit he was trying to fix for us, wasn't he?

Do the meters "drift" that much? Is there an easier way to check them?

ps: Sounds like some constructive work, thanks!

 

[Brad Christy]

Deleted post,

We don't have the smiley I need right now............

Thanks. Brad.

Titan Racing Components

BlackJacik Hydros

 

[Bart Drieghe]

I'm interested to see the results of this , Way to go Don .

@ Brad , while i agree with some remarks , the goal shouldn't be 92 db but WAY BELOW that point . Too many people are focussing on that number but the goal should be doing better and getting it below that number .

In my eyes and little experience , 85 Db with a 15 cc should be a fair limit .

Good luck with trying to find a solution !!

B

 

[Watercadet]

Don, Love ya man, I just have to wonder why we care about a uni-directional sound as apposed to an onmi-directional sound.From what I understand the noise rule is there to keep people from getting annoyed with our boats and to protect our own hearing. That understood, what does it matter what sound the boat makes 1) by itself 2) in a straight line from the meter and 3) in a certain direction? I would think that the "real world" db measurements would need to be taken as a human ear would function-in an omni-directional pick up, which would include a type of din that the uni-directional mic would not account for.

Well Adam you're right, it is all about quieting the boats down & I wish it was that easy. However, since one of the main arguements was that you can't measure sound accurately outdoors, we needed some factual information & that came in the form of the ANSI S1.4-1983 standard. This is the standard now in place for race tracks, drag strips & such that are implementing sound level limits and with them being surrounded by lots of concrete & steel I can't think of a venue more affected by reflected sound. The meter from the Bayer Corp. is fully ANSI compliant & is unidirectional so that's the benchmark we need to use. The cool thing is that, so far, the mega buck ANSI meter & the calibrated R/S meter with the silicone extension have read the same in initial side by side testing. Is this alot of extra work, you bet but I want to have the technical data & real world results, not a bunch of he said, she said stuff. And for the record this is not the only thing "in process" on this rule, more will follow.

And BTW- for those who can test this out this weekend I also ask that you set the meter on a one or two inch thick piece of soft foam on a stable platform to measure as opposed to a tripod and have the pickup end out past the edge of the foam. One thing that has come up is that an improperly counterbalanced and/or being too rigidly mounted on the tripod can actually increase your readings. A piece of soft foam is cheap & simple way to eliminate that variable. B)

That makes perfect sence! Thanks!

 

[Don Ferrette]

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

Well?? Any results John? :huh:

 

[John Knight]

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

Well?? Any results John? :huh:

It was very windy Saturday and not sure how much, if any effect, it had. Meter was on a 3" block of foam near the start line pointed directly to the course. No wind shield was used. Took measurements twice of 2 boats during the calmest periods I could get. Got about 3/4 laps without the coupler and then 3/4 laps with. Every case, the measurement with the coupler was 3-5 db LOUDER than without. It is certainly more focused that way but louder with the results.

Is that what you expected to see?

 

[Don Ferrette]

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

Well?? Any results John? :huh:

It was very windy Saturday and not sure how much, if any effect, it had. Meter was on a 3" block of foam near the start line pointed directly to the course. No wind shield was used. Took measurements twice of 2 boats during the calmest periods I could get. Got about 3/4 laps without the coupler and then 3/4 laps with. Every case, the measurement with the coupler was 3-5 db LOUDER than without. It is certainly more focused that way but louder with the results.

Is that what you expected to see?

How far from the boat were you typically measuring, which way was the wind blowing in relation to the meter and lastly has it been checked and/or calibrated??

 

[John Knight]

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

Well?? Any results John? :huh:

It was very windy Saturday and not sure how much, if any effect, it had. Meter was on a 3" block of foam near the start line pointed directly to the course. No wind shield was used. Took measurements twice of 2 boats during the calmest periods I could get. Got about 3/4 laps without the coupler and then 3/4 laps with. Every case, the measurement with the coupler was 3-5 db LOUDER than without. It is certainly more focused that way but louder with the results.

Is that what you expected to see?

How far from the boat were you typically measuring, which way was the wind blowing in relation to the meter and lastly has it been checked and/or calibrated??

Boat was running about 60' - 80' generally from the meter, swirling winds but mostly from the right, new meter.

 

[Don Ferrette]

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

Well?? Any results John? :huh:

It was very windy Saturday and not sure how much, if any effect, it had. Meter was on a 3" block of foam near the start line pointed directly to the course. No wind shield was used. Took measurements twice of 2 boats during the calmest periods I could get. Got about 3/4 laps without the coupler and then 3/4 laps with. Every case, the measurement with the coupler was 3-5 db LOUDER than without. It is certainly more focused that way but louder with the results.

Is that what you expected to see?

How far from the boat were you typically measuring, which way was the wind blowing in relation to the meter and lastly has it been checked and/or calibrated??

Boat was running about 60' - 80' generally from the meter, swirling winds but mostly from the right, new meter.

Thanks. Give me a call tonight if you get time.

 

[John Knight]

Will be at the lake tomorrow prepping for the Tunnel Championships. Will try and give it a test run then. Supposed to be rather windy so the conditions may not be favorable for a reasonable test but will try if we can.

Well?? Any results John? :huh:

It was very windy Saturday and not sure how much, if any effect, it had. Meter was on a 3" block of foam near the start line pointed directly to the course. No wind shield was used. Took measurements twice of 2 boats during the calmest periods I could get. Got about 3/4 laps without the coupler and then 3/4 laps with. Every case, the measurement with the coupler was 3-5 db LOUDER than without. It is certainly more focused that way but louder with the results.

Is that what you expected to see?

How far from the boat were you typically measuring, which way was the wind blowing in relation to the meter and lastly has it been checked and/or calibrated??

Boat was running about 60' - 80' generally from the meter, swirling winds but mostly from the right, new meter.

Thanks. Give me a call tonight if you get time.

Regret to say it will have to wait until next week as I am totally swamped with race prep for the Tunnel Championships. Getting to bed well after midnight every night now. You have been there!