kwkarth
Electronics guys... we have our plusses and minuses. With advent of digital everything, we're being phased out
- Joined
- Sep 30, 2001
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I posted this in Headwize and thought it might be beneficial to post here too.
Many of you already know this stuff but I was really bummed to read of Vert's troubles and thought this thread was a good opportunity to share this info I pulled out of a few books, chart, etc that I have around here. To your good auditory health!!
The ear and the perception of sound
THE STUDY OF THE STRUCTURE OF THE EAR IS A STUDY IN PHYSIOLOGY.
THE STUDY of human perception of sound comes under the general heading of psychology.
Psychoacoustics is an inclusive term embracing the physical structure of the ear, the sound pathways, the perception of sound, and their interrelationships. Psychoacoustics, quite a recent term, is especially pertinent to this study because it emphasizes both structure and function of the human ear.
The stimulus sound wave striking the ear sets in motion mechanical movements that result in neuron discharges that find their way to the brain and create a sensation. Then comes the question, "How are these sounds recognized and interpreted?" In spite of vigorous research activities on all aspects of human hearing, our knowledge is still woefully incomplete.
Sensitivity of the ear
The delicate and sensitive nature of our hearing can be underscored dramatically by a little experiment. A bulky door of an anechoic chamber is slowly opened, revealing extremely thick walls, and three-foot wedges of glass fiber, points inward, lining all walls, ceiling, and what could be called the floor, except that you walk on an open steel grillwork.
A chair is brought in, and you sit down. This experiment takes time, and as a result of prior briefing, you lean back, patiently counting the glass fiber wedges to pass the time. It is very eerie in here. The sea of sound and noises of life and activity in which we are normally immersed and of which we are ordinarily scarcely conscious is now conspicuous by its absence.
The silence presses down on you in the tomblike silence, the first 10 minutes pass, then a half hour. New sounds are discovered, sounds that come from within your own body. First, the loud pounding of your heart, still recovering from the novelty of the situation. An hour goes by. The blood coursing through the vessels becomes audible. At last, if your ears are keen, your patience is rewarded by a strange hissing sound between the "ker-bumps" of the heart and the sloshing of blood. What is it? It is the sound of air particles pounding against your eardrums. The eardrum motion resulting from this hissing sound is unbelievably small-only 1/100 of a millionth of a centimeter or 1/10 the diameter of a hydrogen molecule!
Is this awesome or what?
The human ear cannot detect sounds softer than the rain of air particles on the eardrum. This is the threshold of hearing. There would be no reason to have ears more sensitive, because any lower-level sound would be drowned by the air-particle noise. This means that the ultimate sensitivity of our hearing just matches the softest sounds possible in an air medium.
Accident? Adaptation? Design?
At the other extreme, our ears can respond to the roar of a cannon, the noise of a rocket blastoff, or a jet aircraft under full power. Special protective features of the ear protect the sensitive mechanism from damage from all but the most intense noises.
It is worth protecting this wondrous gift of hearing we have.
Occupational and recreational deafness
The hearing of workers in industry is now protected by law. The higher the environmental noise, the less exposure allowed. Nerve deafness resulting from occupational noise is recognized as a distinct health hazard. It is especially bad or someone who works all day in a high-noise environment, afterward engages in motorcycle or automobile racing, then goes home and listens to his cans @ a high level, or spends hours in a club, day after day.
The professional audio engineer operating with high monitoring levels is risking irreparable injury to the basic tools of the trade…his ears. As high-frequency loss creeps in, the volume control is turned up to compensate, and the rate of deterioration is accelerated.
The key to conserving your hearing is moderation. The best diagnostic we have commonly available today is the audiogram. Comparing today's audiogram with earlier ones establishes the trend; if downward, steps can be taken to check it.
An audiogram of an all too typical 50-ish sound engineer type guy in a rock recording studio, would look something like the Big Dipper constellation. His hearing loss, centered on 4 kHz, is the accumulation of many years of listening to high-level sounds in the control room. It is frighteningly easy to do the same or worse damage to your own ears with your headphones in the comfort of your own home.
It's not worth it friends, to take such chance by abusing the very sense that gives you such enjoyment and pleasure.
Enclosed is a table from OSHA noise level exposure standards and following that are some references to help you correlate various loudness levels with your own experience. Another good way to begin to learn how to judge “how loud is loud" is to pick up a cheap sound level meter from your neighborhood Radio Shack. There are two models available, one analog, and one digital. I have had both for years and find them to be roughly equally accurate and actually prefer the analog version for most things I use them for.
Analog: Cat: 33-2050 @ about 40 bucks
( http://www.radioshack.com/product.as...5Fid=33%2D2050 )
and the digital version is Cat: 33-2055 @ about 60 bucks.
( http://www.radioshack.com/product.as...5Fid=33%2D2055 )
Head-Fi member "deepriver" posted an excellent piece "save your hearing" and there refers to ( http://www.digital-recordings.com/ ) where you can pick up a CD which will allow you to conduct your own hearing test.
You can position the microphone end of the TRS Sound level meter right where your ear would be with respect to your headphone can and get an idea of how loud you're listening. Keep in mind this will be most accurate for open cans, less so for sealed cans and won't work at all for something like earbuds or Ety's because there's no way to properly couple the earbud to the mic. The folks at digital-recordings also sell a coupler for the TRS meter to make measuring headphone output more accurate. You can also measure the environment around you with the TRS meter to see how much noise pollution you put up with on a daily basis.
How loud is loud? Here is a chart from OSHA which shows how much exposure to noise is “safe” given in sound level vs. time exposure in a 24 hour period. This applies to headphone listening too!!!!
Ref. OSHA 2206
85 dBA 16 hours
90 dBA 8 hours
92 dBA 6 hours
95 dBA 4 hours
97 dBA 3 hours
100 dBA 2 hours
102 dBA 1.5 hours
105 dBA 1 hours
110 dBA 0.5 hours
115 dBA 0.25 hours or less
Reference sound pressure levels:
Saturn Rocket @ Launch (one atmosphere)194 dBA
Ram Jet 160 dBA
Propeller Aircraft 140 dBA
Threshold of pain 135 dBA
Riveter 120 dBA
Heavy Truck 100 dBA
Noisy Office/Heavy Traffic 80 dBA
Conversational Speech 60 dBA
Private office 50 dBA
Quiet Residence 40 dBA
Recording Studio 30 dBA
Leaves Rustling 20 dBA
Hearing threshold, good ears @ frequency of maximum sensitivity (~3kHz) 10 dBA
Hearing threshold, excellent ears @ frequency of maximum sensitivity (~3kHz) 0 dBA
Happy Listening Y'all!
Many of you already know this stuff but I was really bummed to read of Vert's troubles and thought this thread was a good opportunity to share this info I pulled out of a few books, chart, etc that I have around here. To your good auditory health!!
The ear and the perception of sound
THE STUDY OF THE STRUCTURE OF THE EAR IS A STUDY IN PHYSIOLOGY.
THE STUDY of human perception of sound comes under the general heading of psychology.
Psychoacoustics is an inclusive term embracing the physical structure of the ear, the sound pathways, the perception of sound, and their interrelationships. Psychoacoustics, quite a recent term, is especially pertinent to this study because it emphasizes both structure and function of the human ear.
The stimulus sound wave striking the ear sets in motion mechanical movements that result in neuron discharges that find their way to the brain and create a sensation. Then comes the question, "How are these sounds recognized and interpreted?" In spite of vigorous research activities on all aspects of human hearing, our knowledge is still woefully incomplete.
Sensitivity of the ear
The delicate and sensitive nature of our hearing can be underscored dramatically by a little experiment. A bulky door of an anechoic chamber is slowly opened, revealing extremely thick walls, and three-foot wedges of glass fiber, points inward, lining all walls, ceiling, and what could be called the floor, except that you walk on an open steel grillwork.
A chair is brought in, and you sit down. This experiment takes time, and as a result of prior briefing, you lean back, patiently counting the glass fiber wedges to pass the time. It is very eerie in here. The sea of sound and noises of life and activity in which we are normally immersed and of which we are ordinarily scarcely conscious is now conspicuous by its absence.
The silence presses down on you in the tomblike silence, the first 10 minutes pass, then a half hour. New sounds are discovered, sounds that come from within your own body. First, the loud pounding of your heart, still recovering from the novelty of the situation. An hour goes by. The blood coursing through the vessels becomes audible. At last, if your ears are keen, your patience is rewarded by a strange hissing sound between the "ker-bumps" of the heart and the sloshing of blood. What is it? It is the sound of air particles pounding against your eardrums. The eardrum motion resulting from this hissing sound is unbelievably small-only 1/100 of a millionth of a centimeter or 1/10 the diameter of a hydrogen molecule!
Is this awesome or what?
The human ear cannot detect sounds softer than the rain of air particles on the eardrum. This is the threshold of hearing. There would be no reason to have ears more sensitive, because any lower-level sound would be drowned by the air-particle noise. This means that the ultimate sensitivity of our hearing just matches the softest sounds possible in an air medium.
Accident? Adaptation? Design?
At the other extreme, our ears can respond to the roar of a cannon, the noise of a rocket blastoff, or a jet aircraft under full power. Special protective features of the ear protect the sensitive mechanism from damage from all but the most intense noises.
It is worth protecting this wondrous gift of hearing we have.
Occupational and recreational deafness
The hearing of workers in industry is now protected by law. The higher the environmental noise, the less exposure allowed. Nerve deafness resulting from occupational noise is recognized as a distinct health hazard. It is especially bad or someone who works all day in a high-noise environment, afterward engages in motorcycle or automobile racing, then goes home and listens to his cans @ a high level, or spends hours in a club, day after day.
The professional audio engineer operating with high monitoring levels is risking irreparable injury to the basic tools of the trade…his ears. As high-frequency loss creeps in, the volume control is turned up to compensate, and the rate of deterioration is accelerated.
The key to conserving your hearing is moderation. The best diagnostic we have commonly available today is the audiogram. Comparing today's audiogram with earlier ones establishes the trend; if downward, steps can be taken to check it.
An audiogram of an all too typical 50-ish sound engineer type guy in a rock recording studio, would look something like the Big Dipper constellation. His hearing loss, centered on 4 kHz, is the accumulation of many years of listening to high-level sounds in the control room. It is frighteningly easy to do the same or worse damage to your own ears with your headphones in the comfort of your own home.
It's not worth it friends, to take such chance by abusing the very sense that gives you such enjoyment and pleasure.
Enclosed is a table from OSHA noise level exposure standards and following that are some references to help you correlate various loudness levels with your own experience. Another good way to begin to learn how to judge “how loud is loud" is to pick up a cheap sound level meter from your neighborhood Radio Shack. There are two models available, one analog, and one digital. I have had both for years and find them to be roughly equally accurate and actually prefer the analog version for most things I use them for.
Analog: Cat: 33-2050 @ about 40 bucks
( http://www.radioshack.com/product.as...5Fid=33%2D2050 )
and the digital version is Cat: 33-2055 @ about 60 bucks.
( http://www.radioshack.com/product.as...5Fid=33%2D2055 )
Head-Fi member "deepriver" posted an excellent piece "save your hearing" and there refers to ( http://www.digital-recordings.com/ ) where you can pick up a CD which will allow you to conduct your own hearing test.
You can position the microphone end of the TRS Sound level meter right where your ear would be with respect to your headphone can and get an idea of how loud you're listening. Keep in mind this will be most accurate for open cans, less so for sealed cans and won't work at all for something like earbuds or Ety's because there's no way to properly couple the earbud to the mic. The folks at digital-recordings also sell a coupler for the TRS meter to make measuring headphone output more accurate. You can also measure the environment around you with the TRS meter to see how much noise pollution you put up with on a daily basis.
How loud is loud? Here is a chart from OSHA which shows how much exposure to noise is “safe” given in sound level vs. time exposure in a 24 hour period. This applies to headphone listening too!!!!
Ref. OSHA 2206
85 dBA 16 hours
90 dBA 8 hours
92 dBA 6 hours
95 dBA 4 hours
97 dBA 3 hours
100 dBA 2 hours
102 dBA 1.5 hours
105 dBA 1 hours
110 dBA 0.5 hours
115 dBA 0.25 hours or less
Reference sound pressure levels:
Saturn Rocket @ Launch (one atmosphere)194 dBA
Ram Jet 160 dBA
Propeller Aircraft 140 dBA
Threshold of pain 135 dBA
Riveter 120 dBA
Heavy Truck 100 dBA
Noisy Office/Heavy Traffic 80 dBA
Conversational Speech 60 dBA
Private office 50 dBA
Quiet Residence 40 dBA
Recording Studio 30 dBA
Leaves Rustling 20 dBA
Hearing threshold, good ears @ frequency of maximum sensitivity (~3kHz) 10 dBA
Hearing threshold, excellent ears @ frequency of maximum sensitivity (~3kHz) 0 dBA
Happy Listening Y'all!
