In article 3F486347.FCDD5A7F@ieee.org, Jerry Avins at jya@ieee.org wrote on 08/24/2003 03:03:> robert bristow-johnson wrote: >> >> Jerry Avins <jya@ieee.org> wrote in message >> news:<3F465150.E2667543@ieee.org>... >>...>>> How does semantics enter into this? >> >> probably in what we mean by "Doppler Effect". what you mean, if i read this >> right, is an operator that operates on a speed, m, as an input and barfs out >> f' - f as an output. >> >> my semantic regarding the definition of the Doppler Effect is a system that >> when given an input signal of x(t), something like >> >> y(t) = x(t/(1-m)) > > I assumed that x(t) was some quantity x that is a function of time. Was > I wrong?no. but not just *any* function of time. i am viewing x(t) as the "transmitted" sound signal that is getting Doppler shifted.> For simplicity in talking about pitch, we seemed to be talking > about sine waves. What does x(t/(1-m)) represent? What other function of > time are you representing here?x(t) is the source audio that is moving toward the observer at normalized speed of m. x(t/(1-m)) was meant to be the audio that the observer hears (assuming all frequencies propagate at the same speed, c), but i forgot to put in delay and amplitude scaling so y(t) = (A*r(0)/r(t))*x(t/(1-m) - r(0)/c) where r(t) is the distance the source is away from the observer at time t. the amplitude scaling is not inverse square because x(t) and y(t) are not power or intensity functions but are the instantaneous pressure deviation from atmospheric that would be roughly translated to the microphone voltage if a transducer was the "observer". m = -r'(t)/c which is being assumed constant by me at the moment. i guess that makes r(t) = r(0) - m*c*t in this example.>> >> comes out. >> >> if given x1(t) + x2(t) as input then >> >> y(t) = y1(t) + y2(t) >> >> comes out where >> >> y1(t) = x1(t/(1-m)) and y2(t) = x2(t/(1-m)) >> >> i look at m and f and f' (or f'-f) as parameters or properties of the system >> (or "effect"), input, and output respectively. given my semantics of what >> the "Doppler Effect" is and what its input and output is, it's a Linear >> Time-Variant system. >> >> In article 3F47CB2A.7BE430FF@ieee.org, Jerry Avins at jya@ieee.org wrote on >> 08/23/2003 16:14: >> >>> Side puzzler. If my ice cream vendor's Pachelbel drops an octave as he >>> goes by, how fast is he going? :-) >> >> lessee: assuming you survive getting runned over by the truck, f' = f/(1-m) >> when he's moving toward you, and f' = f/(1+m) when he's moving away. so >> somehow, i guess, >> >> f/(1-m) = 2 * f/(1+m) >> or >> 1+m = 2*(1-m) >> >> m = 1 - 2*m >> >> 3*m = 1 >> >> m = 1/3 >> >> so >> >> v = c/3, over 100 m/s. >> >> so maybe you don't survive the passing of the truck. >> >> maybe some formula-1 Indie 500 car sells ice cream and has loudspeakers >> playing Pachebel's Canon on it, but it would have to be scooting fully flat >> out to drop it an octave. >> >> r b-j > > I wondered how they got the exhaust to sound sl lo with the engines > screaming! > > I don't get what you mean because I'm interpreting your symbols wrong. > What I'm getting at is that a plot of m/(1-m) vs. m from m = -1 to +1 is > hardly a straight line. What else does "linear with m" mean? > > Jerry
Is the Doppler effect really linear?
Started by ●August 19, 2003
Reply by ●August 25, 20032003-08-25
Reply by ●August 25, 20032003-08-25
robert bristow-johnson wrote:>... We're getting in pretty deep, and I think drifting away from the question. As I see it, the amount of Doppler shift is not a linear function of speed when the source moves. Superposition holds for different frequencies, but not for different velocities. You haven't contradicted that, but you haven't agreed, either. What say? When speed and pitch are steady, what varies with time? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 25, 20032003-08-25
Jerry Avins wrote:> robert bristow-johnson wrote: > > ... > > We're getting in pretty deep, and I think drifting away from the > question. As I see it, the amount of Doppler shift is not a linear > function of speed when the source moves. Superposition holds for > different frequencies, but not for different velocities. You haven't > contradicted that, but you haven't agreed, either. What say? > > When speed and pitch are steady, what varies with time? > > JerrySlant Range Slant Range Rate Slant Range acceleration Cross Range Cross Range Rate Cross Range acceleration Bearing Bearing rate Bearing acceleration Phase Received Amplitude (I've neglected elevation and its associated rates)
Reply by ●August 25, 20032003-08-25
In article bidd5u$jkv$1@newslocal.mitre.org, Stan Pawlukiewicz at stanp@nospam_mitre.org wrote on 08/25/2003 12:23:> Jerry Avins wrote: >> robert bristow-johnson wrote: >> >> ... >> >> We're getting in pretty deep, and I think drifting away from the >> question. As I see it, the amount of Doppler shift is not a linear >> function of speed when the source moves. Superposition holds for >> different frequencies, but not for different velocities. You haven't >> contradicted that, but you haven't agreed, either. What say? >> >> When speed and pitch are steady, what varies with time? >> >> Jerry > > Slant Range > Slant Range Rate > Slant Range acceleration > Cross Range > Cross Range Rate > Cross Range acceleration > Bearing > Bearing rate > Bearing acceleration > Phase > Received Amplitude > > (I've neglected elevation and its associated rates) >how about Delay? r b-j
Reply by ●August 25, 20032003-08-25
On Thu, 21 Aug 2003 13:48:36 -0400, Stan Pawlukiewicz <stanp@nospam_mitre.org> wrote:>Eric Jacobsen wrote: >> >> There's actually a lot of information about the situation that can be >> obtained merely by observing the Doppler history of things moving >> around you (this was the topic of my MS thesis). Back in the day I >> set out to show that one could even determine how far away the emitter >> was by the Doppler history observed at a single sensor (i.e., >> microphone). After some initial failed attempts I told my advisor >> that I was going to drop that parameter from my analysis, and he >> emphatically replied in his Korean accent, "No! Must do range!" I >> then set out to prove that range could not be determined in this >> manner and after a weekend hunched over a pad of engineering paper I >> had an algorithm for determining range from the Doppler observation. >> It worked pretty well. >> >> So my effort to prove that it couldn't be done failed, too. >> >> >> Eric Jacobsen >> Minister of Algorithms, Intel Corp. >> My opinions may not be Intel's opinions. >> http://www.ericjacobsen.org > >There's a derivation in Quinn and Hannan's "The Estimation and Tracking > of Frequency"Although I am a great admirer of Barry's work I often have a hard time following his papers, and definitely his book. There is, in fact, a derivation in Chapter 1 of the book, and I've stared at it a while and don't have a clue how one would go about estimating velocity or range with it. Perhaps I'm thick, but for the most part Barry's approach to problems is fairly orthogonal to mine. That's okay, though, and he's a math/stats whiz for sure. My thesis was published in 1990, so I didn't have the benefit of any of the work that has come along since. The more recent techniques certainly work better, too. Mine had difficulty at low SNR or if the emitter spectrum didn't have any nice "features" to pick out and track. e.g., I could estimate velocity and range of propeller-driven airplanes and Indy cars pretty well, but B-1Bs were indistinguishable from high-powered noise (which is how they're often described, anyway). My technique had the advantage of being very straightforward and getting decent performance, but it wasn't the sort of thing to use for very high accuracy unless the source was emitting a pure tone. Fun stuff, though. I should've done more with it at the time... Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●August 25, 20032003-08-25
"Clay S. Turner" wrote:> > "Jerry Avins" <jya@ieee.org> wrote in message > news:3F47CB2A.7BE430FF@ieee.org... > >> > > Side puzzler. If my ice cream vendor's Pachelbel drops an octave as he > > goes by, how fast is he going? :-) > > Jerry, > > What's the air temp?? > > Clay > > > -- > > Engineering is the art of making what you want from things you can get. > > �����������������������������������������������������������������������That depends. For a bystander, or the stagnation temperature in the driver's compartment? :-) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 26, 20032003-08-26
Stan Pawlukiewicz wrote:> > Jerry Avins wrote: > > robert bristow-johnson wrote: > > > > ... > > > > We're getting in pretty deep, and I think drifting away from the > > question. As I see it, the amount of Doppler shift is not a linear > > function of speed when the source moves. Superposition holds for > > different frequencies, but not for different velocities. You haven't > > contradicted that, but you haven't agreed, either. What say? > > > > When speed and pitch are steady, what varies with time? > > > > Jerry > > Slant Range > Slant Range Rate > Slant Range acceleration > Cross Range > Cross Range Rate > Cross Range acceleration > Bearing > Bearing rate > Bearing acceleration > Phase > Received Amplitude > > (I've neglected elevation and its associated rates)I thought we restricted the discussion to the case of no proper motion, a moving source directly approaching a stationary observer. That's the simplest case that the formula m/(1 - m) is valid for. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 26, 20032003-08-26
Jerry Avins wrote:> Stan Pawlukiewicz wrote: > >>Jerry Avins wrote: >> >>>robert bristow-johnson wrote: >>> >>> ... >>> >>>We're getting in pretty deep, and I think drifting away from the >>>question. As I see it, the amount of Doppler shift is not a linear >>>function of speed when the source moves. Superposition holds for >>>different frequencies, but not for different velocities. You haven't >>>contradicted that, but you haven't agreed, either. What say? >>> >>>When speed and pitch are steady, what varies with time? >>> >>>Jerry >> >>Slant Range >>Slant Range Rate >>Slant Range acceleration >>Cross Range >>Cross Range Rate >>Cross Range acceleration >>Bearing >>Bearing rate >>Bearing acceleration >>Phase >>Received Amplitude >> >>(I've neglected elevation and its associated rates) > > > I thought we restricted the discussion to the case of no proper motion, > a moving source directly approaching a stationary observer. That's the > simplest case that the formula m/(1 - m) is valid for. > > JerrySorry Jerry, I was (am) a smart ass at times ;)
