- Email: [email protected]
Doppler research in the nineteenth century
Ultrasound in Med. & Bid.. Pergamon Press Ltd.. 1930.
Vol. 6. pp. l-5 Printed in Great Britain
AN HISTORICAL NOTE DOPPLER RESEARCH IN THE NINETEENTH CENTURY E. J. JONKMAN Research Unit TN0 for Clinical Neurophysiology, c/o Westeinde Hospital, Lijnbaan 32,2512 VA The Hague, The Netherlands Key Words: Acoustics, Doppler effect.
The Doppler effect is a rather well known reached in those days was the velocity attained phenomenon: when a wave source is moving on the “iron ways”. As luck would have it only in relation to an observer the perceived wave 2 yr before the railroad between the cities of frequency is different from the emitted Amsterdam and Utrecht had been laid down. A frequency (the perceived frequency being formal requestto the Secretary of Stateof Home higher than the emitted frequency when the Affairs was made. Almost by return mail the source and the observer are moving towards government replied that the railroad would be each other, the perceived frequency being available for experiments after the train of lower than the emitted frequency when the 1.30p.m. had left Utrecht. Apparently the observer and the emitter are moving away railroad traflic had not yet reached an imposing from each other). In 1842 this effect was intensity. It is noteworthy that the government predicted by Doppler on theoretical grounds in those days did not hesitate to stimulate (Doppler, 1842) but not experimentally scientific research in a quick and efficient way. proven. In 1844 Doppler encountered some For the first experiment (February 1845) opposition from the side of the young Dutch Buys Ballot needed two horn players and a scientist C. H. D. Buys Ballot (see Fig. 1). At locomotive. A calibration was made: one that time Buys Ballot was rather unknown, musician blew a note, the other indicated the later on he became a professor of minerology, pitch of the perceived tone. It appeared that geology, chemistry, mathematics and physics both musicians had the sense of absolute successively; he was the founder of the pitch. After this calibration one of the horn Dutch meteorological institute and is well blowers was put on the locomotive (see Fig. known for his law concerning the deviation 2) and the other one posted himself along the of the winds on the northern and southern track. Indeed it appeared that the note blown hemisphere respectively. In his thesis Buys on the locomotive was perceived almost half Ballot postulated the following theorem: a note higher when locomotive and observer “Theoriam Doppleri probandam existimo; ad were approaching each other, and half a note stellarum autem duplicium colores explican- lower when the locomotive drove away from dos non sufficientem dice” or ‘Doppler’s the observer. The experiment had to be theory must be put to the test, I don’t think it aborted after the first measurements because capable of explaining the colours of the of hail and snowstorms. It was decided to double-stars”. As far as we know Doppler did repeat the experiments under conditions of not react at all. ‘beautiful and nice weather”. The first results Buys Ballot, however, thought it necessary were published in less than one month after to test Doppler’s theory experimentally. To the experiments. This first publication was prove the Doppler effect the relative velocity sent not to a physics periodical but to a of the emitter (or observer) ought to be of the journal for music lovers (Buys Ballot, 1845 same order of magnitude as the velocity of the a). The experiments were repeated on 3 June wave phenomenon under study. Even as far as 1845. That day the weather was almost too sound is concerned there was hardly any hot: the brass horns were almost put out of experimental set-up feasible in the 19th cen- tune in the bright sunshine. The experiment tury. The maximum velocity that could be was now much more refined. Along the track UMB
Vol. 6. No.
I-A
1
E. J.
2
JONKMAN
three teams were stationed (see Fig. 3, point A, B and C) composed of a hornblower, an observer and a kind of stage manager. Such a team was also put on a flat top car behind the locomotive. Buys Ballot himself stood next to the engineer on the locomotive (Buys Ballot, 1845 B). A horn was blown on the train while approaching a station and after passing it (arrows with “I” in Fig. 3). The tones were perceived and noted down at the stations. A horn was sounded at the stations when the train passed the station (arrows “A”, “B” and “C” in Fig. 3). The musicians tried to score the tones in sixteenths of one note (this appeared to be impossible; the 8nal score was made in eighths of one note). During the day the train made a number of runs along the track, each time after a long “take off’ in order to obtain a more or less constant velocity. A large number of observations was made. Because in the year 1845 the unit of frequency (Herz) was not yet postulated, it was impossible for Buys Ballot to measure the absolute frequency of the tones. The height of the tones was put arbitrarily at a “wave number of 1000”. The results obtained, corrected for sound velocity changes with temperature and atmospheric pressure, showed a remarkably good correlation with the results to be expected on theoretical grounds. It had been intended to do a more sophisticated experiment: blow the same note simultaneously at stations “A” and “B” (lower line in Fig. 3) and try to observe a dissonance on the train while moving away from “B” and towards “C”. This experiment was omitted because there was no way to score the expected dissonance. Buys Ballot pointed out that there were certain weak
ES wird
gebhsen
et al.
spots in his experiments, the implications of which are remarkable: 1. The sound intensity of the horns was relatively low compared with the background noise (locomotive, wind). This was partially corrected by using a more powerful instrument in the later runs (signal horn instead of key bugle). 2. One experiment was made useless by an interfering signal: during one run the engineer blew the stream whistle, some observers scored rather remarkable notes during that run. 3. The speed of the train was relatively low compared with the velocity of sound. The resulting measuring error could be halved when two trains could be used moving towards another. Buys Ballot regretted that there was no doubletrack available in the Netherlands at that time. 4. The Doppler effect is dependent on the angle between the direction of observation and the direction of the moving object. Buys Ballot real&d that this angle ought to be as small as possible. This resulted in his order to the observers that they should stand not more than one yard from the track and the moving train. After evaluation of the results it appeared that the Doppler effect could be clearly demonstrated and roughly measured. Nowadays we can make an estimate in Hz of the height of the notes blown by the musicians (g). Using Buys Ballot’s observations we can calculate the speed of the train which appeared to have been 18.3 m/set. Buys Ballot measured 20.0 mlsec, so the measuring error in these experiments was less than 10%. Although these experiments were rather successful, Buys Ballot devoted himself to
in:
-___ ~__~~___f_~___t_-~__~___L
A
L
6
L
____ c--_-__c_-_~c_-____~c_~~ A
L
L
C
--_-t_ BA
L
BC
L
---C
Fig. 3. Original drawing by Buys Ballot of his experiments (retouched) (“es wird geblasen” = “one blows at”). U = Utrecht, M = village of Maamen. For explanation see text.
Doppler research in the nineteenth
century
Fig. 1. C. H. D. Buys Ballot (1817~1890).
Fig. 2. Model of the locomotive (named “Hercules”) used in the first experiments. Dutch Railroad Museum)
(By courtesy of the
Doppler research in the nineteenth century
theoretical science during the rest of his life. He never did any other experimental work and never showed any interest in sound research afterwards. REFERENCES Buys Ballot, C. H. D. (I 845a) Bedrog van het gehoororgaan in het bepalen van de hoogte van een
5
waargenomen toon. Caecilia. Algemeen Muzikaal Tijdschrift van Nederland. Tweede jaargang, No.7, 78-81. Buys Ballot, C. H. D. (l845b) Akustische Versuche auf der Niederiindischen Eisenbahn, nebst gelegentlichen Bemerkungen zur Theorie des Herrn Prof. Doppler. Pogg. Ann. Bd. LXVI, 1845 no. 11: 321-351. Doppler, C. Ueber das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels. Abh Kgl Biihm Ges Wissench (Prag), 1842, pp 465-482.
Vol. 6. pp. l-5 Printed in Great Britain
AN HISTORICAL NOTE DOPPLER RESEARCH IN THE NINETEENTH CENTURY E. J. JONKMAN Research Unit TN0 for Clinical Neurophysiology, c/o Westeinde Hospital, Lijnbaan 32,2512 VA The Hague, The Netherlands Key Words: Acoustics, Doppler effect.
The Doppler effect is a rather well known reached in those days was the velocity attained phenomenon: when a wave source is moving on the “iron ways”. As luck would have it only in relation to an observer the perceived wave 2 yr before the railroad between the cities of frequency is different from the emitted Amsterdam and Utrecht had been laid down. A frequency (the perceived frequency being formal requestto the Secretary of Stateof Home higher than the emitted frequency when the Affairs was made. Almost by return mail the source and the observer are moving towards government replied that the railroad would be each other, the perceived frequency being available for experiments after the train of lower than the emitted frequency when the 1.30p.m. had left Utrecht. Apparently the observer and the emitter are moving away railroad traflic had not yet reached an imposing from each other). In 1842 this effect was intensity. It is noteworthy that the government predicted by Doppler on theoretical grounds in those days did not hesitate to stimulate (Doppler, 1842) but not experimentally scientific research in a quick and efficient way. proven. In 1844 Doppler encountered some For the first experiment (February 1845) opposition from the side of the young Dutch Buys Ballot needed two horn players and a scientist C. H. D. Buys Ballot (see Fig. 1). At locomotive. A calibration was made: one that time Buys Ballot was rather unknown, musician blew a note, the other indicated the later on he became a professor of minerology, pitch of the perceived tone. It appeared that geology, chemistry, mathematics and physics both musicians had the sense of absolute successively; he was the founder of the pitch. After this calibration one of the horn Dutch meteorological institute and is well blowers was put on the locomotive (see Fig. known for his law concerning the deviation 2) and the other one posted himself along the of the winds on the northern and southern track. Indeed it appeared that the note blown hemisphere respectively. In his thesis Buys on the locomotive was perceived almost half Ballot postulated the following theorem: a note higher when locomotive and observer “Theoriam Doppleri probandam existimo; ad were approaching each other, and half a note stellarum autem duplicium colores explican- lower when the locomotive drove away from dos non sufficientem dice” or ‘Doppler’s the observer. The experiment had to be theory must be put to the test, I don’t think it aborted after the first measurements because capable of explaining the colours of the of hail and snowstorms. It was decided to double-stars”. As far as we know Doppler did repeat the experiments under conditions of not react at all. ‘beautiful and nice weather”. The first results Buys Ballot, however, thought it necessary were published in less than one month after to test Doppler’s theory experimentally. To the experiments. This first publication was prove the Doppler effect the relative velocity sent not to a physics periodical but to a of the emitter (or observer) ought to be of the journal for music lovers (Buys Ballot, 1845 same order of magnitude as the velocity of the a). The experiments were repeated on 3 June wave phenomenon under study. Even as far as 1845. That day the weather was almost too sound is concerned there was hardly any hot: the brass horns were almost put out of experimental set-up feasible in the 19th cen- tune in the bright sunshine. The experiment tury. The maximum velocity that could be was now much more refined. Along the track UMB
Vol. 6. No.
I-A
1
E. J.
2
JONKMAN
three teams were stationed (see Fig. 3, point A, B and C) composed of a hornblower, an observer and a kind of stage manager. Such a team was also put on a flat top car behind the locomotive. Buys Ballot himself stood next to the engineer on the locomotive (Buys Ballot, 1845 B). A horn was blown on the train while approaching a station and after passing it (arrows with “I” in Fig. 3). The tones were perceived and noted down at the stations. A horn was sounded at the stations when the train passed the station (arrows “A”, “B” and “C” in Fig. 3). The musicians tried to score the tones in sixteenths of one note (this appeared to be impossible; the 8nal score was made in eighths of one note). During the day the train made a number of runs along the track, each time after a long “take off’ in order to obtain a more or less constant velocity. A large number of observations was made. Because in the year 1845 the unit of frequency (Herz) was not yet postulated, it was impossible for Buys Ballot to measure the absolute frequency of the tones. The height of the tones was put arbitrarily at a “wave number of 1000”. The results obtained, corrected for sound velocity changes with temperature and atmospheric pressure, showed a remarkably good correlation with the results to be expected on theoretical grounds. It had been intended to do a more sophisticated experiment: blow the same note simultaneously at stations “A” and “B” (lower line in Fig. 3) and try to observe a dissonance on the train while moving away from “B” and towards “C”. This experiment was omitted because there was no way to score the expected dissonance. Buys Ballot pointed out that there were certain weak
ES wird
gebhsen
et al.
spots in his experiments, the implications of which are remarkable: 1. The sound intensity of the horns was relatively low compared with the background noise (locomotive, wind). This was partially corrected by using a more powerful instrument in the later runs (signal horn instead of key bugle). 2. One experiment was made useless by an interfering signal: during one run the engineer blew the stream whistle, some observers scored rather remarkable notes during that run. 3. The speed of the train was relatively low compared with the velocity of sound. The resulting measuring error could be halved when two trains could be used moving towards another. Buys Ballot regretted that there was no doubletrack available in the Netherlands at that time. 4. The Doppler effect is dependent on the angle between the direction of observation and the direction of the moving object. Buys Ballot real&d that this angle ought to be as small as possible. This resulted in his order to the observers that they should stand not more than one yard from the track and the moving train. After evaluation of the results it appeared that the Doppler effect could be clearly demonstrated and roughly measured. Nowadays we can make an estimate in Hz of the height of the notes blown by the musicians (g). Using Buys Ballot’s observations we can calculate the speed of the train which appeared to have been 18.3 m/set. Buys Ballot measured 20.0 mlsec, so the measuring error in these experiments was less than 10%. Although these experiments were rather successful, Buys Ballot devoted himself to
in:
-___ ~__~~___f_~___t_-~__~___L
A
L
6
L
____ c--_-__c_-_~c_-____~c_~~ A
L
L
C
--_-t_ BA
L
BC
L
---C
Fig. 3. Original drawing by Buys Ballot of his experiments (retouched) (“es wird geblasen” = “one blows at”). U = Utrecht, M = village of Maamen. For explanation see text.
Doppler research in the nineteenth
century
Fig. 1. C. H. D. Buys Ballot (1817~1890).
Fig. 2. Model of the locomotive (named “Hercules”) used in the first experiments. Dutch Railroad Museum)
(By courtesy of the
Doppler research in the nineteenth century
theoretical science during the rest of his life. He never did any other experimental work and never showed any interest in sound research afterwards. REFERENCES Buys Ballot, C. H. D. (I 845a) Bedrog van het gehoororgaan in het bepalen van de hoogte van een
5
waargenomen toon. Caecilia. Algemeen Muzikaal Tijdschrift van Nederland. Tweede jaargang, No.7, 78-81. Buys Ballot, C. H. D. (l845b) Akustische Versuche auf der Niederiindischen Eisenbahn, nebst gelegentlichen Bemerkungen zur Theorie des Herrn Prof. Doppler. Pogg. Ann. Bd. LXVI, 1845 no. 11: 321-351. Doppler, C. Ueber das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels. Abh Kgl Biihm Ges Wissench (Prag), 1842, pp 465-482.