You know if people would read and quit flapping there lips they may learn something. All of this stuff that the new board members are trying to do has already been done or researched. Now we are bring Osha into this again. These standards are based on noise that is indoors unless you have a piece of equipment that is a very high noise level outside. Every industrial plant that I have been into has hearing protection indoors but not outside unless there is a turbine or jet engine setting outdoors running and therefore you will wear hearing protection when you are within so many feet of these units. But this is not osha that is doing this but the companys themselves. Also if you go and read the osha standards you will find the word "Otolaryngologist"
used many times in "Audiometric testing programs" that test the employees for hearing baseline. Now Dr. Gary Turner wrote a piece that was place in the Roostertail a couple of years ago called the "Nature of Sound". He did not make any of this stuff up but had it on file in is office because of his practice. Maybe some of you read it maybe some of you did not and there again maybe you did not know what you read. But I will show it to you again to refresh you memory.
SOUND
I have been asked by several individuals to write an article about sound. Recently there has much been said about the issue of sound. I am not an expert on the physics of sound but deal with subject daily in my practice as an OTOLARYNGOLOGIST AND HEAD AND NECK SURGEON, referred to as ENT.
Sound is measured in dB, which is a logarithmic value. We speak of the frequency in term of hertz[Hz]. When an audiogram is done it is usually performed in a sound proof booth and frequencies of 250htz to 4000 and sometimes 8000htz are tested. When the test is done the individual resounds to the test stimuli at various dB’s, the intent being to establish the slightest intensity that can be heard. This establishes the PURE TONE THRESHOLD. The PTAs the average of the 500,1000 and 2000 Hz and a PTT greater than 25db is considered abnormal. The problem is that noise induced hearing loss generally is seen in the higher frequencies. There the could be a 60 dB threshold for 4000 and 8000 Hz and a PTA of 15db. It is also well known that presbycusis which the term for nerve hearing loss of aging occurs in the higher frequencies.
Sound is a complicated entity. When we measure hearing we use a PURE TONE. Pure tones are not pleasing. A pure tone is a sine wave of compression and rarefaction of air molecules. An example of a pure tone is a 512 tuning fork. This is “middle C” on the piano, but is does sound like a piano. When a trumpet, flute,saxaphone and trombone play “middle C,512htz” that they sound differently. This is due to the “overtones,other small sine waves on top for the 512 sine wave that gives the quality and timbre that identifies the individual instruments.
The human ear consists of the outer ear, which consists of the pinna and the external auditory canal. The middle ear which consists of the eardrum and ossicles,malleous-hammer.incus-anvil, and stapes-stirrup. The inner which consist of the cochlea and the 8th cranial nerve. The cochlea is a transducer that converts sound vibratory mechanical energy to electrical energy and the nerve conducts to the hearing center in the brain. It is important to note that CHILDRENS EARS ARE MUCH MORE EFFICIENT IN THE CONDUCTION OF SOLUND TO THE COCHLEA THAN ADULTS. Children’s ossicles are not as stiff as adults and are much more susceptible to noise induced hearing loss.
When discussing hearing loss we speak of sensory-neural ,conductive and mixed hearing loss. SN deals primarily with loss of function of the cochlea the nerve or both. Conductive hearing loss is the reduced ability to get sound to the inner hearing mechanism. Wax build up,hole in the eardrum, fluid in the middle ear can produce this type of loss. Mixed represents a combination of both,ie, an elderly person with nerve loss who gets a stopped up ear after an airplane flight.
Sound in general is a wonderful thing Helen Keller was asked at one time which of her sense she would like to have back if possible and it was the ability to hear! The question is when is there TOO MUCH sound. In general if one has to shout to make someone hear you in a noisy environment there maybe too much sound. Too much sound is irritating. A screaming baby will raise a parent’s heart rate. The lack of sound is frightening as often occurs just before a tornado is about to hit and there are no birds chirping and no dogs barking, you better seek cover. It was vary strange for me at 13,000 ft and there was no sound just my heart beating in my ears at a plateau of untouched snow and blue sky.
The AUDIOLOGIST DESK REFERENCE pg. 670, has the OSHA 1983 guidelines which are used today.”In an 8hr period one can sustain 4hrs of CONTINOUS noise of 95db, 92 dB for 6.2 hrs. On pg. 683, the following typical dB readings were listed: Heavy traffic 80db, elevated train 80db, and a symphony orchestra 100db. A vary IMPORTANT question is whether sound and noise is additive? For example if two boats each produce 100db, then two running at the same time produce 200db? The answer is NO! In the AUDIOLOGIST DESK REFERENCE, page 687,”Sound sources combine their sound POWER[rather than pressure.” There is a MULTIPLIER rule 2x=3db,3.16x=5db,10x=11db. Therefore if a boat produces 90db, two similar boats would produce 93db.
In the same text on page 686”The amount of power[e.g.,sound intensity at a microphone]at various distance from the sound source will vary inversely with the square of the distance.” This occurs if there is no barrier such as trees, cars and etc. Refer to the figure 6-12 and the first paragraph, taken from the text THE NATURE OF SOUND. This basically states that at twice the radius from where the intensity is measured the intensity will be ¼ of the baseline measurement. Thus if a boat is measured at 50ft. and the dB level is 95db, it will be 27.5 dB.
MY OPINION
The following is my opinion based on the above information on some of the discussions that has recently surface with respect to ANOTHER RULE with respect to sound.
1. I think IMPBA should be concerned about the level of sound that the participants are subjected to. This is especially the case with young children. It should be ADVISED that children in the pits should wear hearing protection. Adults are not more likely to “break their hearing bones” than children. Also we do not exceed OSHA levels because the exposure is not continuos 95db for 4hrs. The hearing protection for children should be advised.
2. The proposed measuring technique is flawed since the distance at which the measurement is taken is not constant. Slight change in the distance of the measurement from the boat produces dramatic change in the dB level recorded.
3. The recommendation to advance from 95db to 92 dB is laudable, however the human ear can not reliably detect a three-dB change.
4. I do not believe a dB RULE WILL SAVE PONDS. Again based on the above physics of sound if a reading of the dB level in the yard of a nearby house where complaints have arisen is taken while boats are running even 6 boats at a time, there will be no measurable increase in dB level above the ambient levels. In fact we did such a test at our pond in B’ham and the results where as stated. The issue is that we can detect a SOUND or LACK of sound that is different from the ambient sounds. I can hear a person’s generator a block away but there is no increase in the dB level at my house. We will loose ponds where house have encroached on our running sites whether we have a dB rule or not
5. I think the present rule is quite adequate and has resulted in reduction of the level of sound at the race site and in the pits.
I hope this information is useful and informative.
Dr. Gary Turner
The Nature of Sound Intensity
Since intensity is the rate of energy flow per unit of area of surface receiving the flow, it follows that, as the distance from the sound source increases, the distribution of energy flow must necessarily decrease. The wave front of a spherical sound wave, as it advances, is a sphere of increasing area, 4 pr², where r is the radius (equal to the distance from the sound source). If the total quantity of energy at the sound source is P, the energy crossing a unit of area of surface would be P/4 pr². From this it is apparent that the intensity of a sound wave varies inversely as the square of the distance from the source, or I=1/d². A sound with an intensity, I, at a certain distance from the source will have one-fourth the intensity at twice the distance and one-sixteenth the intensity at four times the distance. This relationship, known as the inverse square law, is one of the fundamental laws of physics and is illustrated in figure 6-12.
A = area r = radius
Figure 6-12 Schematic illustration of the principle of the inverse square law.
Ideally sound intensity is inversely proportion to the square of the distance from the source.
Note: This information was quoted from the book The Nature of Sound pg. 419
So as you can see we have done the math and dotted to "I's" and crossed the "T's". And now they are going to try to reinvent the wheel.
Mark
