Doppler Effect: Listeners Report a Rise the Frequency Lacks

Clip 3 starts near 544 hertz, ends near 463, and never goes up. Each clip is a tone passing at a steady speed in a straight line, in still air, to a listener standing still. Under those conditions the arriving frequency is highest while the source is far off and approaching, and it falls through the whole pass. Listeners in Neuhoff and McBeath's 1996 study still reported a pitch rise on approach; their abstract calls it the Doppler illusion [1].

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Five passes at five speeds

Turn your volume down, then play the clips in order. Each lasts 8 seconds, centered on the moment the source is closest, 10 meters away. Only the speed changes. The level rises and falls with the distance.

Each clip was synthesized for this page from the parameter file below its player, then read back and measured. In all five, the frequency never rose from one 25-millisecond step to the next, and it stayed within 0.03 percent of the prediction. Those checks show that each file matches its parameters. What listeners report is a separate question, answered by the studies further down.

Clip 2 runs at 50 km/h.

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The opening sentence describes clip 3, at 100 km/h.

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Clip 4 runs at 200 km/h.

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Clip 5 runs at 300 km/h. Its fall near the closest point is fast enough to smear inside one 50-millisecond analysis window, so its largest error is the biggest of the five, 0.023 percent.

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Why does the frequency only fall?

Look at the top panel of Figure 6. The arriving frequency depends on how fast the distance between source and listener shrinks or grows, not on the source's speed along its path. Far off, nearly all of clip 3's 27.8 meters per second closes the gap; near the closest point the motion is mostly sideways, and afterward the gap grows faster and faster. So the frequency slides down the whole way instead of jumping.

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For a source in still air and a listener standing still, the arriving frequency is the source frequency × c ÷ (c + u), where c is the speed of sound and u is how fast the distance was growing when that sound left the source. The clips do not apply this formula. They compute when each bit of sound left the source and how far it traveled, and the shift comes out of that delay. The formula's limits for clip 3, 544.0 and 462.6 Hz, are reached only at infinite distance, so the clip starts just below, at 543.9 Hz.

All five clips use 343.2 meters per second, the speed of sound computed for this page for dry air at 20 °C from the ideal-gas formula [2]. Reber and colleagues (2015) expected 345 m/s in air at about 23 °C [3], and the same formula gives 345.0 at that temperature. The entry on gas and vocal resonances works with about the same value for air, and the bat echolocation entry uses 343.2 to time echoes.

Illustration

The clips leave out what a real roadside adds: wind, echoes, and a source whose own tone changes. The effect is named for Christian Doppler.

What do listeners report?

Play clip 3 again and attend to the first 3 seconds. According to their abstract, Neuhoff and McBeath (1996) confirmed that a popular belief exists: the pitch of a moving source rises as it approaches. They also showed that the rise happens in perception, not only in belief [1]. With no matching rise in frequency, they named it the Doppler illusion; under matched static conditions the effect did not occur.

According to the abstract of a 2002 paper by McBeath and Neuhoff, when tones were Doppler shifted so the frequency dropped, judged pitch rose and fell, closely following the change in intensity, the physical strength of the sound [4]. The same abstract reports that a continuous change in intensity can shift pitch about as much as a frequency change approaching an octave. In clip 3 the level climbs about 22 decibels to the closest point and then falls about 20 (Figure 9).

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The spectrum checks cover these files only. Whether you hear a rise in them is a question for listening tests, and the two abstracts describe other sounds and other listeners. The Shepard tone entry is another sound where judged pitch and measured frequency part ways.

How big is the shift at each speed?

The drop from start to end grows with speed, from 0.51 semitones at 20 km/h to 8.57 at 300 km/h. A semitone is one twelfth of an octave, so the drop is 12 × log₂(start ÷ end).

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For scale, Fung and colleagues (2025) tested 16 adults aged 18 to 32, who heard three steady pure tones near 400 Hz and picked the one that differed [5]. On average, their threshold, the difference they could pick out about 71 percent of the time, was 2.34 percent (standard deviation 2.03), about 0.40 semitones. They were tested remotely, at home or another quiet place, over headphones. That threshold is for steady tones heard one after another, not one tone sliding past, so it does not settle whether clip 1's 0.51-semitone fall is noticeable.

Data: five-speed table (CSV) (CSV) (where the data come from and its license, JSON) and reference values (CSV) (CSV) (where the data come from and its license, JSON) Data: Yue, Y., Dong, Z., & Qi, Z.-m. (2025). Acoustic Fabry–Perot resonance detector for passive acoustic thermometry and sound source localization. Sensors 25(8): 2445, equation 6 and the text after it. https://doi.org/10.3390/s25082445, CC BY 4.0; Fung, J., Whiteford, K. L., Mehta, A. H., & Lau, B. K. (2025). Pitch perception in school-aged children: Pure tones, resolved and unresolved harmonics. JASA Express Letters 5(1): 014403, Table 1. https://doi.org/10.1121/10.0034894, CC BY 4.0.

Sources

1. Neuhoff, J. G., & McBeath, M. K. (1996). The Doppler illusion: The influence of dynamic intensity change on perceived pitch. Journal of Experimental Psychology: Human Perception and Performance 22(4): 970–985. Open the sourceRead: abstract only
2. Yue, Y., Dong, Z., & Qi, Z.-m. (2025). Acoustic Fabry–Perot resonance detector for passive acoustic thermometry and sound source localization. Sensors 25(8): 2445. Open the sourceRead: full textText license: CC BY 4.0
3. Reber, S. A., Nishimura, T., Janisch, J., Robertson, M., & Fitch, W. T. (2015). A Chinese alligator in heliox: formant frequencies in a crocodilian. Journal of Experimental Biology 218(15): 2442–2447. Open the sourceRead: full textText license: CC BY 3.0
4. McBeath, M. K., & Neuhoff, J. G. (2002). The Doppler effect is not what you think it is: Dramatic pitch change due to dynamic intensity change. Psychonomic Bulletin & Review 9(2): 306–313. Open the sourceRead: abstract only
5. Fung, J., Whiteford, K. L., Mehta, A. H., & Lau, B. K. (2025). Pitch perception in school-aged children: Pure tones, resolved and unresolved harmonics. JASA Express Letters 5(1): 014403. Open the sourceRead: full textText license: CC BY 4.0

Sense check:

One step, under a minute

Turn your volume down, play clip 5 once, then find on Figure 5 the moment the frequency falls fastest. Check whether that is the moment the source is closest to you. Next: Shepard tone · Bat echolocation

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Cite this page

Tricks of Ear and Eye. "Doppler Effect: Listeners Report a Rise the Frequency Lacks." Tricks of Ear and Eye. Published 2026-10-30. https://tricksofearandeye.com/sound/doppler-effect/. Accessed on the date you read it.