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#1
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Radio Shack Sound Level Meter
I have recently bought a Radio Shack Digital Sound Level Meter. It has a
facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Hank |
#2
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Radio Shack Sound Level Meter
Call Radio Shack!
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Hank |
#3
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Radio Shack Sound Level Meter
Call Radio Shack!
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Hank |
#4
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Radio Shack Sound Level Meter
Call Radio Shack!
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Hank |
#5
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Radio Shack Sound Level Meter
The calibration of the meter is referenced in a calibrated standard test
chamber using calibrated standard referencing equipment. Using it in a normal room or stage setting will be very different. I will give you an equivalent, according to the effects of the acoustics of the environment. The sound source that you are using is bouncing around off of objects in the area, and is not necessarily accurate in itself to begin with. If you read the instruction booklet that came with the meter, you will see that it is fairly complex in many aspects, yet it can be simple to use as a fixed reference for a particular circumstance. As for its response, it should have the options to follow a specific weighted curves. -- Greetings, Jerry Greenberg GLG Technologies GLG ========================================= WebPage http://www.zoom-one.com Electronics http://www.zoom-one.com/electron.htm ========================================= "Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Hank |
#6
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Radio Shack Sound Level Meter
The calibration of the meter is referenced in a calibrated standard test
chamber using calibrated standard referencing equipment. Using it in a normal room or stage setting will be very different. I will give you an equivalent, according to the effects of the acoustics of the environment. The sound source that you are using is bouncing around off of objects in the area, and is not necessarily accurate in itself to begin with. If you read the instruction booklet that came with the meter, you will see that it is fairly complex in many aspects, yet it can be simple to use as a fixed reference for a particular circumstance. As for its response, it should have the options to follow a specific weighted curves. -- Greetings, Jerry Greenberg GLG Technologies GLG ========================================= WebPage http://www.zoom-one.com Electronics http://www.zoom-one.com/electron.htm ========================================= "Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Hank |
#7
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Radio Shack Sound Level Meter
The calibration of the meter is referenced in a calibrated standard test
chamber using calibrated standard referencing equipment. Using it in a normal room or stage setting will be very different. I will give you an equivalent, according to the effects of the acoustics of the environment. The sound source that you are using is bouncing around off of objects in the area, and is not necessarily accurate in itself to begin with. If you read the instruction booklet that came with the meter, you will see that it is fairly complex in many aspects, yet it can be simple to use as a fixed reference for a particular circumstance. As for its response, it should have the options to follow a specific weighted curves. -- Greetings, Jerry Greenberg GLG Technologies GLG ========================================= WebPage http://www.zoom-one.com Electronics http://www.zoom-one.com/electron.htm ========================================= "Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Hank |
#8
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Radio Shack Sound Level Meter
"Jerry G." wrote in message ... The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. LOL, a Radio Shack meter actually calibrated to a reference standard. Were you trying to be funny or just clueless? TonyP. |
#9
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Radio Shack Sound Level Meter
"Jerry G." wrote in message ... The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. LOL, a Radio Shack meter actually calibrated to a reference standard. Were you trying to be funny or just clueless? TonyP. |
#10
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Radio Shack Sound Level Meter
"Jerry G." wrote in message ... The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. LOL, a Radio Shack meter actually calibrated to a reference standard. Were you trying to be funny or just clueless? TonyP. |
#11
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Radio Shack Sound Level Meter
LMAO
"Tony Pearce" wrote in message u... "Jerry G." wrote in message ... The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. LOL, a Radio Shack meter actually calibrated to a reference standard. Were you trying to be funny or just clueless? TonyP. |
#12
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Radio Shack Sound Level Meter
LMAO
"Tony Pearce" wrote in message u... "Jerry G." wrote in message ... The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. LOL, a Radio Shack meter actually calibrated to a reference standard. Were you trying to be funny or just clueless? TonyP. |
#13
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Radio Shack Sound Level Meter
LMAO
"Tony Pearce" wrote in message u... "Jerry G." wrote in message ... The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. LOL, a Radio Shack meter actually calibrated to a reference standard. Were you trying to be funny or just clueless? TonyP. |
#14
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Radio Shack Sound Level Meter
"Jerry G." wrote in message ...
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. Using it in a normal room or stage setting will be very different. I will give you an equivalent, according to the effects of the acoustics of the environment. The sound source that you are using is bouncing around off of objects in the area, and is not necessarily accurate in itself to begin with. If you read the instruction booklet that came with the meter, you will see that it is fairly complex in many aspects, yet it can be simple to use as a fixed reference for a particular circumstance. As for its response, it should have the options to follow a specific weighted curves. Mr. Greenburg, do you EVER bother to actually read the posts you are responding to? The poster had a very specific question about a specific function that is NOT behaving the way expected. Your answer had pretty much nothing to do with his question. As to the question itself, it's not entirely clear, as I have not seen the specific unit, what they mean by a 200 second averaging period. If it means the time constant of the averager is 200 seconds, then it is entirely possible for the behavior you have seen, since the averager is not a fixed time window precisely 200 seconds that excludes information outside that range. Rather, the averager is "leaky" with a decay time of 200 seconds, as one example. When you first turned your noise source on, the value in the averager was 0 and, at the end of the first 100 seconds, you'll have the average over that time, which all things being equal, should be half that of the short-term average value during that 100 seconds. Now, you turn it off for the next 100 seconds, and you'll be averaging that first value with the remainder of the time, where the value is 0. Given that, as a very rough guess, I would expect, then that the value at the end of the first 100 seconds to somewhat less than the full value, maybe like - 6 dB, and the value at the end of 200 seconds to be less, like maybe -12 dB. If you wanted to closer to what you expect, run a constant level noise source for quite a long time, maybe 15 minutes, then shut it off, and examine it 100 seconds later. THat may give you something along the lines you expect. |
#15
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Radio Shack Sound Level Meter
"Jerry G." wrote in message ...
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. Using it in a normal room or stage setting will be very different. I will give you an equivalent, according to the effects of the acoustics of the environment. The sound source that you are using is bouncing around off of objects in the area, and is not necessarily accurate in itself to begin with. If you read the instruction booklet that came with the meter, you will see that it is fairly complex in many aspects, yet it can be simple to use as a fixed reference for a particular circumstance. As for its response, it should have the options to follow a specific weighted curves. Mr. Greenburg, do you EVER bother to actually read the posts you are responding to? The poster had a very specific question about a specific function that is NOT behaving the way expected. Your answer had pretty much nothing to do with his question. As to the question itself, it's not entirely clear, as I have not seen the specific unit, what they mean by a 200 second averaging period. If it means the time constant of the averager is 200 seconds, then it is entirely possible for the behavior you have seen, since the averager is not a fixed time window precisely 200 seconds that excludes information outside that range. Rather, the averager is "leaky" with a decay time of 200 seconds, as one example. When you first turned your noise source on, the value in the averager was 0 and, at the end of the first 100 seconds, you'll have the average over that time, which all things being equal, should be half that of the short-term average value during that 100 seconds. Now, you turn it off for the next 100 seconds, and you'll be averaging that first value with the remainder of the time, where the value is 0. Given that, as a very rough guess, I would expect, then that the value at the end of the first 100 seconds to somewhat less than the full value, maybe like - 6 dB, and the value at the end of 200 seconds to be less, like maybe -12 dB. If you wanted to closer to what you expect, run a constant level noise source for quite a long time, maybe 15 minutes, then shut it off, and examine it 100 seconds later. THat may give you something along the lines you expect. |
#16
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Radio Shack Sound Level Meter
"Jerry G." wrote in message ...
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. The calibration of the meter is referenced in a calibrated standard test chamber using calibrated standard referencing equipment. Using it in a normal room or stage setting will be very different. I will give you an equivalent, according to the effects of the acoustics of the environment. The sound source that you are using is bouncing around off of objects in the area, and is not necessarily accurate in itself to begin with. If you read the instruction booklet that came with the meter, you will see that it is fairly complex in many aspects, yet it can be simple to use as a fixed reference for a particular circumstance. As for its response, it should have the options to follow a specific weighted curves. Mr. Greenburg, do you EVER bother to actually read the posts you are responding to? The poster had a very specific question about a specific function that is NOT behaving the way expected. Your answer had pretty much nothing to do with his question. As to the question itself, it's not entirely clear, as I have not seen the specific unit, what they mean by a 200 second averaging period. If it means the time constant of the averager is 200 seconds, then it is entirely possible for the behavior you have seen, since the averager is not a fixed time window precisely 200 seconds that excludes information outside that range. Rather, the averager is "leaky" with a decay time of 200 seconds, as one example. When you first turned your noise source on, the value in the averager was 0 and, at the end of the first 100 seconds, you'll have the average over that time, which all things being equal, should be half that of the short-term average value during that 100 seconds. Now, you turn it off for the next 100 seconds, and you'll be averaging that first value with the remainder of the time, where the value is 0. Given that, as a very rough guess, I would expect, then that the value at the end of the first 100 seconds to somewhat less than the full value, maybe like - 6 dB, and the value at the end of 200 seconds to be less, like maybe -12 dB. If you wanted to closer to what you expect, run a constant level noise source for quite a long time, maybe 15 minutes, then shut it off, and examine it 100 seconds later. THat may give you something along the lines you expect. |
#17
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Radio Shack Sound Level Meter
Thank you Dick Pierce for your thoughtful reply to my question. Being a
"digital" power meter, I have assumed that the "averaging" process is carried out digitally since we are talking of integration times up to 200 seconds. Presumably, the meter takes the pressure from its microphone, converts that linearly to voltage, then performs the operations of squaring the voltage to get the power, then compressing this power logarithmically to arrive at dBs. Just where in this sequence, the "average" is taken is the point on which I am not clear. More careful experiments, where I took "averages" over times up to 120 seconds while turning the noise source on and off with a 50% duty cycle, yielded an "average" reading that was approximately 6 dB below the noise source power. This would suggest to me that the averaging is being done on the microphone output voltage (half voltage equals -6db power drop). However, It would be great if someone has actual knowledge of the power meter circuitry and its functions. Any offers? Hank |
#18
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Radio Shack Sound Level Meter
Thank you Dick Pierce for your thoughtful reply to my question. Being a
"digital" power meter, I have assumed that the "averaging" process is carried out digitally since we are talking of integration times up to 200 seconds. Presumably, the meter takes the pressure from its microphone, converts that linearly to voltage, then performs the operations of squaring the voltage to get the power, then compressing this power logarithmically to arrive at dBs. Just where in this sequence, the "average" is taken is the point on which I am not clear. More careful experiments, where I took "averages" over times up to 120 seconds while turning the noise source on and off with a 50% duty cycle, yielded an "average" reading that was approximately 6 dB below the noise source power. This would suggest to me that the averaging is being done on the microphone output voltage (half voltage equals -6db power drop). However, It would be great if someone has actual knowledge of the power meter circuitry and its functions. Any offers? Hank |
#19
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Radio Shack Sound Level Meter
Thank you Dick Pierce for your thoughtful reply to my question. Being a
"digital" power meter, I have assumed that the "averaging" process is carried out digitally since we are talking of integration times up to 200 seconds. Presumably, the meter takes the pressure from its microphone, converts that linearly to voltage, then performs the operations of squaring the voltage to get the power, then compressing this power logarithmically to arrive at dBs. Just where in this sequence, the "average" is taken is the point on which I am not clear. More careful experiments, where I took "averages" over times up to 120 seconds while turning the noise source on and off with a 50% duty cycle, yielded an "average" reading that was approximately 6 dB below the noise source power. This would suggest to me that the averaging is being done on the microphone output voltage (half voltage equals -6db power drop). However, It would be great if someone has actual knowledge of the power meter circuitry and its functions. Any offers? Hank |
#20
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Radio Shack Sound Level Meter
"Hank2" wrote in message . com...
Thank you Dick Pierce for your thoughtful reply to my question. Being a "digital" power meter, I have assumed that the "averaging" process is carried out digitally since we are talking of integration times up to 200 seconds. Not necessarily... Presumably, the meter takes the pressure from its microphone, converts that linearly to voltage, then performs the operations of squaring the voltage to get the power, then compressing this power logarithmically to arrive at dBs. Just where in this sequence, the "average" is taken is the point on which I am not clear. Not necessarily. It's also possible that the averaging is, in fact, done with a simple analog leaky integrator with a long enough time constant, and the "digital" portion is nothing more than an inexpensive digital display of the result. They can even get the dB scaling by taking the averaged linear voltage, digitizing it then run it through a ROM lookup table to convert linear volts to dB. Very simple to design, very inexpensive to implement. More careful experiments, where I took "averages" over times up to 120 seconds while turning the noise source on and off with a 50% duty cycle, yielded an "average" reading that was approximately 6 dB below the noise source power. This would suggest to me that the averaging is being done on the microphone output voltage (half voltage equals -6db power drop). Yup, sounds about right. However, It would be great if someone has actual knowledge of the power meter circuitry and its functions. Any offers? Alas, I have no specific knowledge of this unit. |
#21
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Radio Shack Sound Level Meter
"Hank2" wrote in message . com...
Thank you Dick Pierce for your thoughtful reply to my question. Being a "digital" power meter, I have assumed that the "averaging" process is carried out digitally since we are talking of integration times up to 200 seconds. Not necessarily... Presumably, the meter takes the pressure from its microphone, converts that linearly to voltage, then performs the operations of squaring the voltage to get the power, then compressing this power logarithmically to arrive at dBs. Just where in this sequence, the "average" is taken is the point on which I am not clear. Not necessarily. It's also possible that the averaging is, in fact, done with a simple analog leaky integrator with a long enough time constant, and the "digital" portion is nothing more than an inexpensive digital display of the result. They can even get the dB scaling by taking the averaged linear voltage, digitizing it then run it through a ROM lookup table to convert linear volts to dB. Very simple to design, very inexpensive to implement. More careful experiments, where I took "averages" over times up to 120 seconds while turning the noise source on and off with a 50% duty cycle, yielded an "average" reading that was approximately 6 dB below the noise source power. This would suggest to me that the averaging is being done on the microphone output voltage (half voltage equals -6db power drop). Yup, sounds about right. However, It would be great if someone has actual knowledge of the power meter circuitry and its functions. Any offers? Alas, I have no specific knowledge of this unit. |
#22
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Radio Shack Sound Level Meter
"Hank2" wrote in message . com...
Thank you Dick Pierce for your thoughtful reply to my question. Being a "digital" power meter, I have assumed that the "averaging" process is carried out digitally since we are talking of integration times up to 200 seconds. Not necessarily... Presumably, the meter takes the pressure from its microphone, converts that linearly to voltage, then performs the operations of squaring the voltage to get the power, then compressing this power logarithmically to arrive at dBs. Just where in this sequence, the "average" is taken is the point on which I am not clear. Not necessarily. It's also possible that the averaging is, in fact, done with a simple analog leaky integrator with a long enough time constant, and the "digital" portion is nothing more than an inexpensive digital display of the result. They can even get the dB scaling by taking the averaged linear voltage, digitizing it then run it through a ROM lookup table to convert linear volts to dB. Very simple to design, very inexpensive to implement. More careful experiments, where I took "averages" over times up to 120 seconds while turning the noise source on and off with a 50% duty cycle, yielded an "average" reading that was approximately 6 dB below the noise source power. This would suggest to me that the averaging is being done on the microphone output voltage (half voltage equals -6db power drop). Yup, sounds about right. However, It would be great if someone has actual knowledge of the power meter circuitry and its functions. Any offers? Alas, I have no specific knowledge of this unit. |
#23
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Radio Shack Sound Level Meter
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Possibly, I am misunderstanding your question. But what it is averaging is dBSPL (Sound Pressure Level), which is not power. What it should have indicated, if your timing was accurate and the unit is reasonably well calibrated is a loss of 6dB for your test procedure. 8dB isn't all that bad considering the "quality" of the equipment in question. ;-) |
#24
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Radio Shack Sound Level Meter
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Possibly, I am misunderstanding your question. But what it is averaging is dBSPL (Sound Pressure Level), which is not power. What it should have indicated, if your timing was accurate and the unit is reasonably well calibrated is a loss of 6dB for your test procedure. 8dB isn't all that bad considering the "quality" of the equipment in question. ;-) |
#25
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Radio Shack Sound Level Meter
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Possibly, I am misunderstanding your question. But what it is averaging is dBSPL (Sound Pressure Level), which is not power. What it should have indicated, if your timing was accurate and the unit is reasonably well calibrated is a loss of 6dB for your test procedure. 8dB isn't all that bad considering the "quality" of the equipment in question. ;-) |
#26
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Radio Shack Sound Level Meter
"Hank2" wrote in message . com... I have recently bought a Radio Shack Digital Sound Level Meter. It has a facility for taking "average" readings over periods up to 200 seconds. I tried an experiment where I performed an "average" over a set period during which, for half of the time I turned the noise source off. Instead of indicating and average equal to 3db below the source power, a drop of around 8db showed up. Obviously it was not averaging power. Other tests where I varied the sound source power during the averaging period, showed that the meter was not indicating average db readings either. If the "average" indicated is not of power, nor of dbs, just what is it? An explanation would be much appreciated. Possibly, I am misunderstanding your question. But what it is averaging is dBSPL (Sound Pressure Level), which is not power. What it should have indicated, if your timing was accurate and the unit is reasonably well calibrated is a loss of 6dB for your test procedure. 8dB isn't all that bad considering the "quality" of the equipment in question. ;-) |
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