Are any airplane manufacturers working on quieter sub-sonic planes?
The short answer is "yes"
.
The long answer is "yes, but it's proving to be very difficult."
It used to be that the primary cause of (commercial) jet noise was the engines. Manufacturers have managed to reduce the acoustic output from the engines (somewhat:) through engineering and operation changes (see here for example).
Other challenges include aerodynamic noise and structure-borne noise. Aerodynamic noise reduction can hopefully be achieved through shape changes. Structure-borne noise is a little difficult because it's difficult to mitigate without adding weight to the plane.
My personal feeling is that structure-borne noise reduction can be accomplished using active-vibration reduction, but then again, I'm more of a surface-transportation noise-guy than an aero/astro noise guy.
erm, no you cannot transcode a fairplay aac file to a mp3 file. You can burn it to a cd, and then rip it, but a direct transcode is not possible.
You can't transcode a Fairplay AAC file to mp3 directly in iTunes, but if you know how to access the QuickTime API using Applescript, RealBasic or Apple's tools, you can transcode the files easily.
Also, you may be able to transoce Fairplay files using digital audio editing software that uses QuickTime.
The first 2 sources indicate that many Mac/Lisa GUI concepts that are commonly attributed to Xerox either came from Apple researchers or predated both PARC & Apple. The third source indicates that Mac and Lisa development predated the PARC visit.
The statement "Fact: Apple came to the GUI via Xerox, after attending a PARC presentation which convinced them it was a good idea" is wrong as all of these sources point out. If you have evidence to the contrary, please share it. Otherwise, I'm done here.
Thus Horn is more correct than he knew when he wrote that the world has generally overestimated the influence of PARC on the Mac, as even some of the concepts that he attributes to PARC's influence predated PARC.
The duration of a train traveling at 60 mph is more annoying than a Maglev train of equal length travling 250 mph, simply because you have to put up with it longer.
You're correct that duration is one component that makes noise annoying, but sound level also contributes. A long event with low noise level can be more annoying that a short event with higher sound level. In the case of a Maglev at 250 mph, it would be so much louder than the slow moving train, that it would still be more annoying. Plus you have the 'startle' effect caused by the rapid onset of the sound level.
Even though they don't have wheels, they still require large engines for power generation. So right there you've got most of the same noise a traditional train makes.
Not exactly. Maglev's are driven by electricity (electro magnets), and the generators are placed at substations along the guideway. So there is no "generation" noise that you hear from the vehicle (although part of the noise you hear from the maglev is attributable to the switching noise of the magnets and stator spacing).
Now your 'transformer buzz' comment is relevant. As I said, the power is generated and distributed at power substations along the guideway. When the train is accelerating along the guideway, the substations have to crank up the power, and they get pretty loud.
You can grab some more clips here (scroll down to the Ground-Borne Vibration Characteristics of Acela and TransRapid TR08 Maglev presentation about halfway down).
Sorry, no sound, my Olympus C2040 only does video.
(note that I'm the author of presentation and I took the videos, but I don't work at that company anymore).
Though they suggest unfamilliarity, one might wonder if it's more of a frequency/pitch or timbre issue.
Having heard the TR08, I tend to disagree - the suckers are just loud at top speeds (although at low speeds, say <100mph, they are almost whisper quiet).
One unanticipated effect is that at high speeds, the Maglev sound has a rapid onset, which causes a 'startle' effect. Basically, one moment your environment is quiet, the next moment it's very loud, and the moment after that it's quiet again as the vehicle recedes. This might be part of the problem.
The FRA high-speed train noise guidelines try to account for this.
Why are they so loud at night? I know trains run through the city here regularly, and I can't hear the train whistles where I live during the day, even though I know they still toot them, but at night I can here the trains that have got to be at least ten miles from here. Why is that?
If there is a large body of water between you and the train tracks, or if you're in an area with weird cooling characteristics, you might be hearing the effects of a temperature inversion.
Air temperatures right above large bodies of water tend to be cooler then the surrounding air. Similarly, there might be some areas near you that cool more rapidly at night than other areas. These effects cause layers of air at different temperatures, which set up an impedance mismatch.
Sound that travels through the air bounce off these temperature inversions, which can 'bend' sound toward you. Combine this effect with lower ambient noise levels at night, and you find that you can sometime hear noise sources at far distances.
You would be suprised at the different materials conventional speaker cones are made from. You've probably seen plastic and paper cones. Probably even a few different types of plastics.
Everything from paper to polypropylene to Kevlar
Speaker cones have to low resonance or at least a very narrow frequency range they resonate in.
This depends on a lot of things. A speaker driver cone by itself has a particular resonance frequency. The sharpness (or 'Q') of the resonance is dependent on the mass of the cone, and the stiffness of the surround.
However, once you put the speaker driver into an enclosure of finite volume (like a box), the resonance changes. The amount of the resonance change, and the new Q depends on the driver parameters, and the box parameters (size, port dimensions, stuffing, etc). For some low-frequency speaker designs (notably the band-pass designs popularized by Bose and boomcars) you want the resonance - that's how you get your output. Other designs (like my own, see my web page if you're interested), try to minimize the Q while still designing for an extended bass response. It's all about give and take.
Generally you try to stay away from resonances for mid-range and high-frequency speakers, but much of the time the resonance occurs outside of the frequency range of interest, so it's not a problem. (I suppose it could be a problem if the cross-over design is borked.)
What can be a problem is ugly breakup modes that occur when the speaker driver stops moving as a piston, and starts flexing. This flexing causes sound waves that add and cancel at certain frequencies, resulting in nasty sounds.
Kevlar (yes, the bullet proof vest material) is also a popular material at the moment. B&W and Wharfdale are two companies that make Kevlar based drivers. B&W have some interesting documents on their web site [bwspeakers.com] on what makes it such a good material.
Kevlar was a very popular material in the late 80's/early 90's. It has better moisture resistance than paper cones which helps durability. It's stronger than paper, but that doesn't make a large difference - most of the strength of a driver comes from the conical shape, not the material. Plus, you can corrugate the driver for additional strength. But the added strength does help to reduce the severity of break-up modes. It can't eliminate them however, because the modal behavior is a function of it's size and shape.
Wooden cones would have a nice wide frequency range.
The "frequency range" of wooden (or other cones) is meaningless. A speaker cone is essentially a piston. If it stays rigid, we get well understood pistonic behavior, and all is well. If it breaks up, it sounds like crap. If the material is delicate, it will break. If the material is heavy, the resonance frequency is reduced, and you lose sensitivity. You're changing the mass and strength parameters, which I suppose can have an audible effect. This might be a breakthrough in manufacturing techniques, but this isn't a breakthrough in sound.
I know Bose bashing is always fashionable, but in my experience, the Bose headsets work pretty well. They may or may not be best-in-class, but they most certainly do not "suck."
You'll also notice that your articles are talking about CABLE break in.
Well some of the articles talk about cable break-in, but the search brings up several speaker-specific articles (for exmaple, the topic "Speaker burn-in question"). Dick Pierce's comments are particularly insightful.
No, they mesurably change sound slightly (at least the ones I like). I've checked with actualy measuring equipment.
By how much? (and measured with what?) Enough that the difference can't be attributed to humidty, temperature and ambient pressure differences? Speaker drivers are generally "burned-in" for several hours at the factory as part of the Q/A checks. Any more is redundant.
The noise emitting part of a CPU fan sort of approaches being a point source compared to that So, it should be possible to place the noise canceling speakers at the fan and do a decent job.
Well that's only true is the ANC speaker also acts as a point source, and I doubt there's a speaker driver anywhere that's truly omnidirectional. But if you can funnel the noise in one direction, the task becomes considerably easier
New speakers come from the factory with everything a little tight, as everything does new. Over the first month of playing they slightly change their sound as they get to their normal "burned in" point.
You know the whole "speaker burn-in" thing is pretty much a myth, right? (unless you literally burn out your speaker!)
I thought the noise cancelling headphones worked because they were right against your ears.
Well yes and no. Noise cancelling headsets are particularly effective because the ANC speaker and microphone are right next to your ears. This helps insure that the signal that arrives at your year can be sampled and inverted so that the sum cancels at the ear. It would be much harder to accomplish this with speakers and/or mics located away from the ear.
However, remote mics/speakers may work if the noise source is highly directional, like a waveguide (I suspect that's happening here). If you can effectively cancel the sound at the orifice, you'll probably achieve a significant reduction in transmitted sound, no matter the location of the receiver.
You're talking about masking, which is the practice of "covering" softer sounds with louder sounds. It's one of the acoustic principles that are exploited for perceptual audio codecs.
Near the landing strips you can sometimes find some "sound reflectors" which just reflect the sound wave they receive from the planes. The sound is then canceled by itself.
I think you're referring to a "blast fence." Those have nothing to do with active sound cancellation, they're strictly passive noise control devices that block the path between the noise source and the receiver (just like highway noise barriers). See here or here for examples (the latter is a run-up enclosure, but it's the same principle).
Maglev's are quieter than steel wheel/steel rail trains at similar speeds, but they most certainly do generate significant amounts of noise and vibration, especially at speeds over 180mph.
Instead of buying Universal and being able to bundle a few dozen albums [...]
Instead of spending some of the money they had in the bank, Apple turned digital downloads into a game nobody is going to be able to profit at legally.
Instead of spending some of their money? How about all of their money? They only had $4-5 billion in the bank at the time, and Vivendi was asking $6-7 billion for the music division. Assuming Steve was able to talk them down to $3-4 billion, that would leave Apple with little to no money left over in a bad economy.
The scenario you describe would be cool, but do you think Apple could realistically have pulled it off? And even if Apple did seriously pursue this, how long before MS simply bought all of the other labels using their $50 billion war chest and screwed us all?
Slashdot Mirror
The short answer is "yes"
.The long answer is "yes, but it's proving to be very difficult."
It used to be that the primary cause of (commercial) jet noise was the engines. Manufacturers have managed to reduce the acoustic output from the engines (somewhat :) through engineering and operation changes (see here for example).
Other challenges include aerodynamic noise and structure-borne noise. Aerodynamic noise reduction can hopefully be achieved through shape changes. Structure-borne noise is a little difficult because it's difficult to mitigate without adding weight to the plane.
My personal feeling is that structure-borne noise reduction can be accomplished using active-vibration reduction, but then again, I'm more of a surface-transportation noise-guy than an aero/astro noise guy.
You can't transcode a Fairplay AAC file to mp3 directly in iTunes, but if you know how to access the QuickTime API using Applescript, RealBasic or Apple's tools, you can transcode the files easily.
Also, you may be able to transoce Fairplay files using digital audio editing software that uses QuickTime.
???
The first 2 sources indicate that many Mac/Lisa GUI concepts that are commonly attributed to Xerox either came from Apple researchers or predated both PARC & Apple. The third source indicates that Mac and Lisa development predated the PARC visit.
The statement "Fact: Apple came to the GUI via Xerox, after attending a PARC presentation which convinced them it was a good idea" is wrong as all of these sources point out. If you have evidence to the contrary, please share it. Otherwise, I'm done here.
- July 1979: List project started
- September 1979: Mac project started
- November 1979: Jobs et al visit PARC
sourceno
You're correct that duration is one component that makes noise annoying, but sound level also contributes. A long event with low noise level can be more annoying that a short event with higher sound level. In the case of a Maglev at 250 mph, it would be so much louder than the slow moving train, that it would still be more annoying. Plus you have the 'startle' effect caused by the rapid onset of the sound level.
Not exactly. Maglev's are driven by electricity (electro magnets), and the generators are placed at substations along the guideway. So there is no "generation" noise that you hear from the vehicle (although part of the noise you hear from the maglev is attributable to the switching noise of the magnets and stator spacing).
Now your 'transformer buzz' comment is relevant. As I said, the power is generated and distributed at power substations along the guideway. When the train is accelerating along the guideway, the substations have to crank up the power, and they get pretty loud.
You can grab some more clips here (scroll down to the Ground-Borne Vibration Characteristics of Acela and TransRapid TR08 Maglev presentation about halfway down).
Sorry, no sound, my Olympus C2040 only does video.
(note that I'm the author of presentation and I took the videos, but I don't work at that company anymore).
.Having heard the TR08, I tend to disagree - the suckers are just loud at top speeds (although at low speeds, say <100mph, they are almost whisper quiet).
One unanticipated effect is that at high speeds, the Maglev sound has a rapid onset, which causes a 'startle' effect. Basically, one moment your environment is quiet, the next moment it's very loud, and the moment after that it's quiet again as the vehicle recedes. This might be part of the problem.
The FRA high-speed train noise guidelines try to account for this.
If there is a large body of water between you and the train tracks, or if you're in an area with weird cooling characteristics, you might be hearing the effects of a temperature inversion.
Air temperatures right above large bodies of water tend to be cooler then the surrounding air. Similarly, there might be some areas near you that cool more rapidly at night than other areas. These effects cause layers of air at different temperatures, which set up an impedance mismatch.
Sound that travels through the air bounce off these temperature inversions, which can 'bend' sound toward you. Combine this effect with lower ambient noise levels at night, and you find that you can sometime hear noise sources at far distances.
See here for an explanation.
But there was a "Developer CD" that came with retail versions of OS X.0 and X.2. It didn't come with preloaded versions however.
.My condolences.
Seriously thought, good luck.
(S.B. Course II, '95)Everything from paper to polypropylene to Kevlar
Speaker cones have to low resonance or at least a very narrow frequency range they resonate in.This depends on a lot of things. A speaker driver cone by itself has a particular resonance frequency. The sharpness (or 'Q') of the resonance is dependent on the mass of the cone, and the stiffness of the surround.
However, once you put the speaker driver into an enclosure of finite volume (like a box), the resonance changes. The amount of the resonance change, and the new Q depends on the driver parameters, and the box parameters (size, port dimensions, stuffing, etc). For some low-frequency speaker designs (notably the band-pass designs popularized by Bose and boomcars) you want the resonance - that's how you get your output. Other designs (like my own, see my web page if you're interested), try to minimize the Q while still designing for an extended bass response. It's all about give and take.
Generally you try to stay away from resonances for mid-range and high-frequency speakers, but much of the time the resonance occurs outside of the frequency range of interest, so it's not a problem. (I suppose it could be a problem if the cross-over design is borked.)
What can be a problem is ugly breakup modes that occur when the speaker driver stops moving as a piston, and starts flexing. This flexing causes sound waves that add and cancel at certain frequencies, resulting in nasty sounds.
Kevlar (yes, the bullet proof vest material) is also a popular material at the moment. B&W and Wharfdale are two companies that make Kevlar based drivers. B&W have some interesting documents on their web site [bwspeakers.com] on what makes it such a good material.Kevlar was a very popular material in the late 80's/early 90's. It has better moisture resistance than paper cones which helps durability. It's stronger than paper, but that doesn't make a large difference - most of the strength of a driver comes from the conical shape, not the material. Plus, you can corrugate the driver for additional strength. But the added strength does help to reduce the severity of break-up modes. It can't eliminate them however, because the modal behavior is a function of it's size and shape.
Wooden cones would have a nice wide frequency range.The "frequency range" of wooden (or other cones) is meaningless. A speaker cone is essentially a piston. If it stays rigid, we get well understood pistonic behavior, and all is well. If it breaks up, it sounds like crap. If the material is delicate, it will break. If the material is heavy, the resonance frequency is reduced, and you lose sensitivity. You're changing the mass and strength parameters, which I suppose can have an audible effect. This might be a breakthrough in manufacturing techniques, but this isn't a breakthrough in sound.
They've been around for some time. They're called "paper cones"
I know Bose bashing is always fashionable, but in my experience, the Bose headsets work pretty well. They may or may not be best-in-class, but they most certainly do not "suck."
Well some of the articles talk about cable break-in, but the search brings up several speaker-specific articles (for exmaple, the topic "Speaker burn-in question"). Dick Pierce's comments are particularly insightful.
No, they mesurably change sound slightly (at least the ones I like). I've checked with actualy measuring equipment.By how much? (and measured with what?) Enough that the difference can't be attributed to humidty, temperature and ambient pressure differences? Speaker drivers are generally "burned-in" for several hours at the factory as part of the Q/A checks. Any more is redundant.
Well that's only true is the ANC speaker also acts as a point source, and I doubt there's a speaker driver anywhere that's truly omnidirectional. But if you can funnel the noise in one direction, the task becomes considerably easier
.You know the whole "speaker burn-in" thing is pretty much a myth, right? (unless you literally burn out your speaker!)
Well yes and no. Noise cancelling headsets are particularly effective because the ANC speaker and microphone are right next to your ears. This helps insure that the signal that arrives at your year can be sampled and inverted so that the sum cancels at the ear. It would be much harder to accomplish this with speakers and/or mics located away from the ear.
However, remote mics/speakers may work if the noise source is highly directional, like a waveguide (I suspect that's happening here). If you can effectively cancel the sound at the orifice, you'll probably achieve a significant reduction in transmitted sound, no matter the location of the receiver.
You're talking about masking, which is the practice of "covering" softer sounds with louder sounds. It's one of the acoustic principles that are exploited for perceptual audio codecs.
I think you're referring to a "blast fence." Those have nothing to do with active sound cancellation, they're strictly passive noise control devices that block the path between the noise source and the receiver (just like highway noise barriers). See here or here for examples (the latter is a run-up enclosure, but it's the same principle).
They settled out of court.
Wrong and wrong(MS Word documents).
Maglev's are quieter than steel wheel/steel rail trains at similar speeds, but they most certainly do generate significant amounts of noise and vibration, especially at speeds over 180mph.
Instead of buying Universal and being able to bundle a few dozen albums [...]
Instead of spending some of the money they had in the bank, Apple turned digital downloads into a game nobody is going to be able to profit at legally.
Instead of spending some of their money? How about all of their money? They only had $4-5 billion in the bank at the time, and Vivendi was asking $6-7 billion for the music division. Assuming Steve was able to talk them down to $3-4 billion, that would leave Apple with little to no money left over in a bad economy.
The scenario you describe would be cool, but do you think Apple could realistically have pulled it off? And even if Apple did seriously pursue this, how long before MS simply bought all of the other labels using their $50 billion war chest and screwed us all?