RF vs. audio of the same frequency
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From an article by an engineer at Cisco Systems:
An RF signal can have the same frequency as a sound wave, and most people can hear a 5 kHz audio tone. No one can hear a 5 kHz RF signal.
Why not?
rf
add a comment |Â
up vote
7
down vote
favorite
From an article by an engineer at Cisco Systems:
An RF signal can have the same frequency as a sound wave, and most people can hear a 5 kHz audio tone. No one can hear a 5 kHz RF signal.
Why not?
rf
1
Hi, For readers who may want to see more of the context of that quotation, can you edit the question and add a link to the original source, please? I found it in a couple of places, and I don't want to add a different source to yours. Thanks :-)
â SamGibson
14 hours ago
Yes - here is the original pdf written by Ron Hranac - scte.org/TechnicalColumns/â¦
â Ben S
4 hours ago
add a comment |Â
up vote
7
down vote
favorite
up vote
7
down vote
favorite
From an article by an engineer at Cisco Systems:
An RF signal can have the same frequency as a sound wave, and most people can hear a 5 kHz audio tone. No one can hear a 5 kHz RF signal.
Why not?
rf
From an article by an engineer at Cisco Systems:
An RF signal can have the same frequency as a sound wave, and most people can hear a 5 kHz audio tone. No one can hear a 5 kHz RF signal.
Why not?
rf
rf
edited 27 secs ago
SamGibson
10k41435
10k41435
asked 17 hours ago
Ben S
563
563
1
Hi, For readers who may want to see more of the context of that quotation, can you edit the question and add a link to the original source, please? I found it in a couple of places, and I don't want to add a different source to yours. Thanks :-)
â SamGibson
14 hours ago
Yes - here is the original pdf written by Ron Hranac - scte.org/TechnicalColumns/â¦
â Ben S
4 hours ago
add a comment |Â
1
Hi, For readers who may want to see more of the context of that quotation, can you edit the question and add a link to the original source, please? I found it in a couple of places, and I don't want to add a different source to yours. Thanks :-)
â SamGibson
14 hours ago
Yes - here is the original pdf written by Ron Hranac - scte.org/TechnicalColumns/â¦
â Ben S
4 hours ago
1
1
Hi, For readers who may want to see more of the context of that quotation, can you edit the question and add a link to the original source, please? I found it in a couple of places, and I don't want to add a different source to yours. Thanks :-)
â SamGibson
14 hours ago
Hi, For readers who may want to see more of the context of that quotation, can you edit the question and add a link to the original source, please? I found it in a couple of places, and I don't want to add a different source to yours. Thanks :-)
â SamGibson
14 hours ago
Yes - here is the original pdf written by Ron Hranac - scte.org/TechnicalColumns/â¦
â Ben S
4 hours ago
Yes - here is the original pdf written by Ron Hranac - scte.org/TechnicalColumns/â¦
â Ben S
4 hours ago
add a comment |Â
4 Answers
4
active
oldest
votes
up vote
17
down vote
The audio tone is compression waves traveling through air that your ears can pick up. The RF signal is waves in the electromagnetic field that you ears have no way of picking up.
2
Powerful ELF-EMF might rattle your fillings.
â amI
15 hours ago
add a comment |Â
up vote
8
down vote
RF signals are electromagnetic (EM) waves. We do not have any sensors for 5 kHz EM waves.
We do have EM sensors though, our eyes. They can sense EM waves from $4ÃÂ10^14$ Hz (red light) to $8ÃÂ10^14$ Hz (violet light). If strong enough we can also feel infrared radiation as heat.
We can also feel (as heat) powerful EM radiation at lower frequencies, but if you feel that then the field is dangerously strong and you should step out of that (radar) beam.
I think this reminder that we can sense EM with our eyes, helped clarify it for me. Also, that RF can be sensed by us as heat - when testing RF circuits at work we must take care not to make contact or we can be burned by the RF.
â Ben S
3 hours ago
add a comment |Â
up vote
5
down vote
Our body is a dielectric (insulator) with salts (conductive ions) so, although we cannot detect EM waves, the absorption of electric fields is generally proportional to the frequency.
Conversely, electric fields can be tolerated with increased levels as the frequency is reduced.
Example bass woofer audio at 60 Hz with 100 mV into the speaker coil is loud enough to be clearly heard and 100Â Vpp might rattle something on the walls.
While a 100 V/m 50 or 60 Hz electric field does nothing to us as not only are we tiny compared to the wavelength in xx km the impedance of our 100 pF fingertip is about 50 Mé, but the salt and an arc can reduce a wire contact to 50 ké easily.
You can easily detect 50~100Â Vpp just by touching a 10:1 scope probe without touching the earth ground, which then shunts the electric field to ground.
This means we can conduct it easily, but not absorb it as a high impedance electric field. We are low impedance as the antenna impedance of our boy is proportional to the super long EM wavelength at the speed of light.
Sound pressures on the other hand in the air are pressure waves and are easily detected by the cilia hairs in our ears, which have progressive different lengths acting as resonators. Below 20 Hz we generally feel the vibrations more than hear them.
Both RF impedances then reduces with increasing surface area into capacitors below antenna wavelengths, but in effect, we act as a weak coupling capacitor to low frequency so there is no energy absorption. It just passed through us. At higher radio and TV frequency at the sub millivolt signal levels we can act as an antenna without the sensation except for possibly better reception. However our energy SAR absorption acceptable rate is a function of frequency and watts/cm3 for a given volume of flesh with a certain "skin depth".
Anecdotal
Back in the 1970s our company designed and made 50Â W and 100Â W VHF and UHF transmitters. Even with the lid open for fine-tuning, and some low stray leakage, the tech's eyes would get bloodshot after a day's work on the production line. So the lid was redesigned with a tuning hole for a plastic screwdriver.
We had all the US military handbooks in our library for aerospace design, so after graduation in the late 1970s, this is how I first learned about human susceptibility to RF spectrum levels.
My first design project there as a young graduate was for a five-channel Doppler tracking Rx using US Navy transmitters around the western hemisphere with a Tx power about 1 megawatt suitable for 100 baud submarine communication all using carriers synchronized like GPS using nuclear clocks (Cesium). All I used was a 2Â m (polar bear proof) whip antenna in the Beaufort Sea on an ice flow to track weather and ice movement in the 1970s.
add a comment |Â
up vote
3
down vote
This is an interesting question because I used to wonder the same thing (no, I'm saying it's an interesting question because of my former curiosity).
You're confusing electromagnetic radiation (something radio produces) with pressure waves (something sound produces). Our ears cannot adjust to electromagnetic waves and they are certain not sensitive to changes in electromagnetic waves.
Another way to look at it is that electromagnetic waves don't have nearly enough force to cause the ear drum to vibrate... whereas sound waves do.
If you want to get on a very quantum level about this, think about how strong gluons are.
add a comment |Â
4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
17
down vote
The audio tone is compression waves traveling through air that your ears can pick up. The RF signal is waves in the electromagnetic field that you ears have no way of picking up.
2
Powerful ELF-EMF might rattle your fillings.
â amI
15 hours ago
add a comment |Â
up vote
17
down vote
The audio tone is compression waves traveling through air that your ears can pick up. The RF signal is waves in the electromagnetic field that you ears have no way of picking up.
2
Powerful ELF-EMF might rattle your fillings.
â amI
15 hours ago
add a comment |Â
up vote
17
down vote
up vote
17
down vote
The audio tone is compression waves traveling through air that your ears can pick up. The RF signal is waves in the electromagnetic field that you ears have no way of picking up.
The audio tone is compression waves traveling through air that your ears can pick up. The RF signal is waves in the electromagnetic field that you ears have no way of picking up.
answered 17 hours ago
evildemonic
935417
935417
2
Powerful ELF-EMF might rattle your fillings.
â amI
15 hours ago
add a comment |Â
2
Powerful ELF-EMF might rattle your fillings.
â amI
15 hours ago
2
2
Powerful ELF-EMF might rattle your fillings.
â amI
15 hours ago
Powerful ELF-EMF might rattle your fillings.
â amI
15 hours ago
add a comment |Â
up vote
8
down vote
RF signals are electromagnetic (EM) waves. We do not have any sensors for 5 kHz EM waves.
We do have EM sensors though, our eyes. They can sense EM waves from $4ÃÂ10^14$ Hz (red light) to $8ÃÂ10^14$ Hz (violet light). If strong enough we can also feel infrared radiation as heat.
We can also feel (as heat) powerful EM radiation at lower frequencies, but if you feel that then the field is dangerously strong and you should step out of that (radar) beam.
I think this reminder that we can sense EM with our eyes, helped clarify it for me. Also, that RF can be sensed by us as heat - when testing RF circuits at work we must take care not to make contact or we can be burned by the RF.
â Ben S
3 hours ago
add a comment |Â
up vote
8
down vote
RF signals are electromagnetic (EM) waves. We do not have any sensors for 5 kHz EM waves.
We do have EM sensors though, our eyes. They can sense EM waves from $4ÃÂ10^14$ Hz (red light) to $8ÃÂ10^14$ Hz (violet light). If strong enough we can also feel infrared radiation as heat.
We can also feel (as heat) powerful EM radiation at lower frequencies, but if you feel that then the field is dangerously strong and you should step out of that (radar) beam.
I think this reminder that we can sense EM with our eyes, helped clarify it for me. Also, that RF can be sensed by us as heat - when testing RF circuits at work we must take care not to make contact or we can be burned by the RF.
â Ben S
3 hours ago
add a comment |Â
up vote
8
down vote
up vote
8
down vote
RF signals are electromagnetic (EM) waves. We do not have any sensors for 5 kHz EM waves.
We do have EM sensors though, our eyes. They can sense EM waves from $4ÃÂ10^14$ Hz (red light) to $8ÃÂ10^14$ Hz (violet light). If strong enough we can also feel infrared radiation as heat.
We can also feel (as heat) powerful EM radiation at lower frequencies, but if you feel that then the field is dangerously strong and you should step out of that (radar) beam.
RF signals are electromagnetic (EM) waves. We do not have any sensors for 5 kHz EM waves.
We do have EM sensors though, our eyes. They can sense EM waves from $4ÃÂ10^14$ Hz (red light) to $8ÃÂ10^14$ Hz (violet light). If strong enough we can also feel infrared radiation as heat.
We can also feel (as heat) powerful EM radiation at lower frequencies, but if you feel that then the field is dangerously strong and you should step out of that (radar) beam.
edited 23 mins ago
Peter Mortensen
1,56231422
1,56231422
answered 16 hours ago
Bimpelrekkie
42.2k23790
42.2k23790
I think this reminder that we can sense EM with our eyes, helped clarify it for me. Also, that RF can be sensed by us as heat - when testing RF circuits at work we must take care not to make contact or we can be burned by the RF.
â Ben S
3 hours ago
add a comment |Â
I think this reminder that we can sense EM with our eyes, helped clarify it for me. Also, that RF can be sensed by us as heat - when testing RF circuits at work we must take care not to make contact or we can be burned by the RF.
â Ben S
3 hours ago
I think this reminder that we can sense EM with our eyes, helped clarify it for me. Also, that RF can be sensed by us as heat - when testing RF circuits at work we must take care not to make contact or we can be burned by the RF.
â Ben S
3 hours ago
I think this reminder that we can sense EM with our eyes, helped clarify it for me. Also, that RF can be sensed by us as heat - when testing RF circuits at work we must take care not to make contact or we can be burned by the RF.
â Ben S
3 hours ago
add a comment |Â
up vote
5
down vote
Our body is a dielectric (insulator) with salts (conductive ions) so, although we cannot detect EM waves, the absorption of electric fields is generally proportional to the frequency.
Conversely, electric fields can be tolerated with increased levels as the frequency is reduced.
Example bass woofer audio at 60 Hz with 100 mV into the speaker coil is loud enough to be clearly heard and 100Â Vpp might rattle something on the walls.
While a 100 V/m 50 or 60 Hz electric field does nothing to us as not only are we tiny compared to the wavelength in xx km the impedance of our 100 pF fingertip is about 50 Mé, but the salt and an arc can reduce a wire contact to 50 ké easily.
You can easily detect 50~100Â Vpp just by touching a 10:1 scope probe without touching the earth ground, which then shunts the electric field to ground.
This means we can conduct it easily, but not absorb it as a high impedance electric field. We are low impedance as the antenna impedance of our boy is proportional to the super long EM wavelength at the speed of light.
Sound pressures on the other hand in the air are pressure waves and are easily detected by the cilia hairs in our ears, which have progressive different lengths acting as resonators. Below 20 Hz we generally feel the vibrations more than hear them.
Both RF impedances then reduces with increasing surface area into capacitors below antenna wavelengths, but in effect, we act as a weak coupling capacitor to low frequency so there is no energy absorption. It just passed through us. At higher radio and TV frequency at the sub millivolt signal levels we can act as an antenna without the sensation except for possibly better reception. However our energy SAR absorption acceptable rate is a function of frequency and watts/cm3 for a given volume of flesh with a certain "skin depth".
Anecdotal
Back in the 1970s our company designed and made 50Â W and 100Â W VHF and UHF transmitters. Even with the lid open for fine-tuning, and some low stray leakage, the tech's eyes would get bloodshot after a day's work on the production line. So the lid was redesigned with a tuning hole for a plastic screwdriver.
We had all the US military handbooks in our library for aerospace design, so after graduation in the late 1970s, this is how I first learned about human susceptibility to RF spectrum levels.
My first design project there as a young graduate was for a five-channel Doppler tracking Rx using US Navy transmitters around the western hemisphere with a Tx power about 1 megawatt suitable for 100 baud submarine communication all using carriers synchronized like GPS using nuclear clocks (Cesium). All I used was a 2Â m (polar bear proof) whip antenna in the Beaufort Sea on an ice flow to track weather and ice movement in the 1970s.
add a comment |Â
up vote
5
down vote
Our body is a dielectric (insulator) with salts (conductive ions) so, although we cannot detect EM waves, the absorption of electric fields is generally proportional to the frequency.
Conversely, electric fields can be tolerated with increased levels as the frequency is reduced.
Example bass woofer audio at 60 Hz with 100 mV into the speaker coil is loud enough to be clearly heard and 100Â Vpp might rattle something on the walls.
While a 100 V/m 50 or 60 Hz electric field does nothing to us as not only are we tiny compared to the wavelength in xx km the impedance of our 100 pF fingertip is about 50 Mé, but the salt and an arc can reduce a wire contact to 50 ké easily.
You can easily detect 50~100Â Vpp just by touching a 10:1 scope probe without touching the earth ground, which then shunts the electric field to ground.
This means we can conduct it easily, but not absorb it as a high impedance electric field. We are low impedance as the antenna impedance of our boy is proportional to the super long EM wavelength at the speed of light.
Sound pressures on the other hand in the air are pressure waves and are easily detected by the cilia hairs in our ears, which have progressive different lengths acting as resonators. Below 20 Hz we generally feel the vibrations more than hear them.
Both RF impedances then reduces with increasing surface area into capacitors below antenna wavelengths, but in effect, we act as a weak coupling capacitor to low frequency so there is no energy absorption. It just passed through us. At higher radio and TV frequency at the sub millivolt signal levels we can act as an antenna without the sensation except for possibly better reception. However our energy SAR absorption acceptable rate is a function of frequency and watts/cm3 for a given volume of flesh with a certain "skin depth".
Anecdotal
Back in the 1970s our company designed and made 50Â W and 100Â W VHF and UHF transmitters. Even with the lid open for fine-tuning, and some low stray leakage, the tech's eyes would get bloodshot after a day's work on the production line. So the lid was redesigned with a tuning hole for a plastic screwdriver.
We had all the US military handbooks in our library for aerospace design, so after graduation in the late 1970s, this is how I first learned about human susceptibility to RF spectrum levels.
My first design project there as a young graduate was for a five-channel Doppler tracking Rx using US Navy transmitters around the western hemisphere with a Tx power about 1 megawatt suitable for 100 baud submarine communication all using carriers synchronized like GPS using nuclear clocks (Cesium). All I used was a 2Â m (polar bear proof) whip antenna in the Beaufort Sea on an ice flow to track weather and ice movement in the 1970s.
add a comment |Â
up vote
5
down vote
up vote
5
down vote
Our body is a dielectric (insulator) with salts (conductive ions) so, although we cannot detect EM waves, the absorption of electric fields is generally proportional to the frequency.
Conversely, electric fields can be tolerated with increased levels as the frequency is reduced.
Example bass woofer audio at 60 Hz with 100 mV into the speaker coil is loud enough to be clearly heard and 100Â Vpp might rattle something on the walls.
While a 100 V/m 50 or 60 Hz electric field does nothing to us as not only are we tiny compared to the wavelength in xx km the impedance of our 100 pF fingertip is about 50 Mé, but the salt and an arc can reduce a wire contact to 50 ké easily.
You can easily detect 50~100Â Vpp just by touching a 10:1 scope probe without touching the earth ground, which then shunts the electric field to ground.
This means we can conduct it easily, but not absorb it as a high impedance electric field. We are low impedance as the antenna impedance of our boy is proportional to the super long EM wavelength at the speed of light.
Sound pressures on the other hand in the air are pressure waves and are easily detected by the cilia hairs in our ears, which have progressive different lengths acting as resonators. Below 20 Hz we generally feel the vibrations more than hear them.
Both RF impedances then reduces with increasing surface area into capacitors below antenna wavelengths, but in effect, we act as a weak coupling capacitor to low frequency so there is no energy absorption. It just passed through us. At higher radio and TV frequency at the sub millivolt signal levels we can act as an antenna without the sensation except for possibly better reception. However our energy SAR absorption acceptable rate is a function of frequency and watts/cm3 for a given volume of flesh with a certain "skin depth".
Anecdotal
Back in the 1970s our company designed and made 50Â W and 100Â W VHF and UHF transmitters. Even with the lid open for fine-tuning, and some low stray leakage, the tech's eyes would get bloodshot after a day's work on the production line. So the lid was redesigned with a tuning hole for a plastic screwdriver.
We had all the US military handbooks in our library for aerospace design, so after graduation in the late 1970s, this is how I first learned about human susceptibility to RF spectrum levels.
My first design project there as a young graduate was for a five-channel Doppler tracking Rx using US Navy transmitters around the western hemisphere with a Tx power about 1 megawatt suitable for 100 baud submarine communication all using carriers synchronized like GPS using nuclear clocks (Cesium). All I used was a 2Â m (polar bear proof) whip antenna in the Beaufort Sea on an ice flow to track weather and ice movement in the 1970s.
Our body is a dielectric (insulator) with salts (conductive ions) so, although we cannot detect EM waves, the absorption of electric fields is generally proportional to the frequency.
Conversely, electric fields can be tolerated with increased levels as the frequency is reduced.
Example bass woofer audio at 60 Hz with 100 mV into the speaker coil is loud enough to be clearly heard and 100Â Vpp might rattle something on the walls.
While a 100 V/m 50 or 60 Hz electric field does nothing to us as not only are we tiny compared to the wavelength in xx km the impedance of our 100 pF fingertip is about 50 Mé, but the salt and an arc can reduce a wire contact to 50 ké easily.
You can easily detect 50~100Â Vpp just by touching a 10:1 scope probe without touching the earth ground, which then shunts the electric field to ground.
This means we can conduct it easily, but not absorb it as a high impedance electric field. We are low impedance as the antenna impedance of our boy is proportional to the super long EM wavelength at the speed of light.
Sound pressures on the other hand in the air are pressure waves and are easily detected by the cilia hairs in our ears, which have progressive different lengths acting as resonators. Below 20 Hz we generally feel the vibrations more than hear them.
Both RF impedances then reduces with increasing surface area into capacitors below antenna wavelengths, but in effect, we act as a weak coupling capacitor to low frequency so there is no energy absorption. It just passed through us. At higher radio and TV frequency at the sub millivolt signal levels we can act as an antenna without the sensation except for possibly better reception. However our energy SAR absorption acceptable rate is a function of frequency and watts/cm3 for a given volume of flesh with a certain "skin depth".
Anecdotal
Back in the 1970s our company designed and made 50Â W and 100Â W VHF and UHF transmitters. Even with the lid open for fine-tuning, and some low stray leakage, the tech's eyes would get bloodshot after a day's work on the production line. So the lid was redesigned with a tuning hole for a plastic screwdriver.
We had all the US military handbooks in our library for aerospace design, so after graduation in the late 1970s, this is how I first learned about human susceptibility to RF spectrum levels.
My first design project there as a young graduate was for a five-channel Doppler tracking Rx using US Navy transmitters around the western hemisphere with a Tx power about 1 megawatt suitable for 100 baud submarine communication all using carriers synchronized like GPS using nuclear clocks (Cesium). All I used was a 2Â m (polar bear proof) whip antenna in the Beaufort Sea on an ice flow to track weather and ice movement in the 1970s.
edited 24 mins ago
Peter Mortensen
1,56231422
1,56231422
answered 15 hours ago
Tony EE rocketscientist
57.6k22082
57.6k22082
add a comment |Â
add a comment |Â
up vote
3
down vote
This is an interesting question because I used to wonder the same thing (no, I'm saying it's an interesting question because of my former curiosity).
You're confusing electromagnetic radiation (something radio produces) with pressure waves (something sound produces). Our ears cannot adjust to electromagnetic waves and they are certain not sensitive to changes in electromagnetic waves.
Another way to look at it is that electromagnetic waves don't have nearly enough force to cause the ear drum to vibrate... whereas sound waves do.
If you want to get on a very quantum level about this, think about how strong gluons are.
add a comment |Â
up vote
3
down vote
This is an interesting question because I used to wonder the same thing (no, I'm saying it's an interesting question because of my former curiosity).
You're confusing electromagnetic radiation (something radio produces) with pressure waves (something sound produces). Our ears cannot adjust to electromagnetic waves and they are certain not sensitive to changes in electromagnetic waves.
Another way to look at it is that electromagnetic waves don't have nearly enough force to cause the ear drum to vibrate... whereas sound waves do.
If you want to get on a very quantum level about this, think about how strong gluons are.
add a comment |Â
up vote
3
down vote
up vote
3
down vote
This is an interesting question because I used to wonder the same thing (no, I'm saying it's an interesting question because of my former curiosity).
You're confusing electromagnetic radiation (something radio produces) with pressure waves (something sound produces). Our ears cannot adjust to electromagnetic waves and they are certain not sensitive to changes in electromagnetic waves.
Another way to look at it is that electromagnetic waves don't have nearly enough force to cause the ear drum to vibrate... whereas sound waves do.
If you want to get on a very quantum level about this, think about how strong gluons are.
This is an interesting question because I used to wonder the same thing (no, I'm saying it's an interesting question because of my former curiosity).
You're confusing electromagnetic radiation (something radio produces) with pressure waves (something sound produces). Our ears cannot adjust to electromagnetic waves and they are certain not sensitive to changes in electromagnetic waves.
Another way to look at it is that electromagnetic waves don't have nearly enough force to cause the ear drum to vibrate... whereas sound waves do.
If you want to get on a very quantum level about this, think about how strong gluons are.
edited 17 hours ago
answered 17 hours ago
KingDuken
1,0802517
1,0802517
add a comment |Â
add a comment |Â
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1
Hi, For readers who may want to see more of the context of that quotation, can you edit the question and add a link to the original source, please? I found it in a couple of places, and I don't want to add a different source to yours. Thanks :-)
â SamGibson
14 hours ago
Yes - here is the original pdf written by Ron Hranac - scte.org/TechnicalColumns/â¦
â Ben S
4 hours ago