Scientists tracked the whales — and recorded a speed almost twice the speed of sound

However, the researchers did not find any violation of the laws of physics. This is not a case of sound or information actually travelling through water at such a speed, but rather an interference effect: the direct signal and its reflection combine in such a way that the maximum of the resulting wave appears earlier than expected. Moreover, this work is currently based on theory and numerical modelling — the effect has yet to be confirmed experimentally.

It all began with an attempt to locate whales more accurately

Oceanographer John Spiceberger of the University of Pennsylvania has been working on the passive acoustic localisation of marine mammals for many years. Instead of searching for the animals visually, researchers install several underwater receivers – hydrophones – and compare the time it takes for the same whale call to reach different points.

This difference can be used to calculate the animal’s position. This approach is particularly useful for whales, which spend a significant amount of time underwater and can be heard over long distances.

However, the method has a physical problem. Sound in the ocean does not necessarily travel from the whale to the hydrophone along a single path. Part of the signal arrives directly, whilst another part may first be reflected off the water’s surface.

Spiesberger’s previous work has already shown that interference between such signals can significantly alter the calculated speed of the acoustic pulse and thus affect the determination of the animal’s coordinates.

It was as if the sound was travelling along two paths simultaneously

This new study focuses on what happens when the direct and reflected signals arrive almost simultaneously.

The effect can be illustrated as follows: a whale emits a sound, and the hydrophone receives two versions of it. The first travels directly to the receiver. The second reaches the ocean’s surface, is reflected off it, and only then reaches the same hydrophone.

These waves are slightly out of phase. When they overlap, interference occurs — amplifying some parts of the signal and attenuating others.

As a result, the shape of the entire pulse changes. Its most pronounced peak may end up in a different place than it would have been for a signal travelling only along the direct path.

The model yielded a result of almost 2,800 metres per second

It was here that the scientists obtained the most striking result.

In one of the simulated scenarios, the speed of sound in water was set at 1,500 m/s. For two model signals, the researchers calculated the speeds at which the maxima appeared as 1,694.5 and 2,782.5 m/s respectively. Both values exceeded the normal speed of sound in the given medium.

In the second case, the value turned out to be approximately 1.85 times higher than the initial 1,500 m/s.

At first glance, it appears as though the sound pulse has somehow broken through its own speed limit. But this is precisely where the key distinction lies between where the peak of the wave packet appears and how quickly new information can be transmitted.

No signal has actually outpaced sound

The authors separately investigated whether this unusual effect could be used to transmit information more quickly.

Their simulations showed that this was not possible.

Although the wave packet’s peak appeared in such a way that the calculated speed exceeded 1,500 m/s, the information was transmitted more slowly than the normal speed of sound. In other words, interference is capable of reshaping the form of a signal that is already propagating, but does not allow a message to be sent that would reach the receiver before the physically permissible moment.

This is precisely why the statement ‘scientists have accelerated sound by almost a factor of two’ would be incorrect. The speed of 2,782.5 m/s relates to a specific method of tracking the position of the wave packet’s peak, rather than to the ultra-fast transmission of information through water.

And what does Einstein’s theory of relativity have to do with this?

This unusual acoustic result prompted the researchers to ask a more fundamental question: could a similar effect occur not only with sound, but also with electromagnetic waves — such as light?

If direct and reflected light signals were to interfere in a similar way, the peak of the wave packet could, in theory, also appear to be travelling faster than light.

However, the authors emphasise that, for electromagnetic waves, this is as yet only a hypothesis, not an experimental result. It has not yet been tested.

Even if the effect can be achieved with light, it will not undermine the special theory of relativity. The researchers’ calculations show that new information cannot be transmitted faster than the speed of light in a vacuum. The first part of the signal capable of carrying new information must still arrive via the usual direct route.

This is precisely where the connection with Einstein’s work lies: a specific part of the waveform may travel or appear unusually quickly, but causality and the fundamental limit on the transmission of information remain intact.

An error could hinder efforts to track whales by their calls

The research also has a very practical side.

When tracking an animal acoustically, its coordinates are often determined by the time difference between the arrival of the same sound at several hydrophones. Such calculations depend on an assumption about the speed of signal propagation.

However, if the position of the pulse peak changes due to interference between the direct and reflected sound, using a standard value for the speed may result in an incorrect estimate of the source’s position.

Previous calculations by Spiesberger and colleagues have already shown that such effects must be taken into account when determining the coordinates of whales based on the arrival times of their signals.

Therefore, the peculiar physics of wave packets may have a very practical application — making acoustic monitoring of marine mammals more accurate.

For now, this is theory, not a sound captured ‘at super-speed’

The study has a fundamental limitation: the result obtained is currently based on theoretical calculations and computer modelling.

The authors explicitly state that the effect requires experimental confirmation. They believe it can be tested for both acoustic and, potentially, electromagnetic waves. For light, for example, a beam could be split into two paths, with one directed straight to the detector and the other via a reflector, after which the signals would be recombined.

Therefore, the current result cannot be described as an experimental detection of sound actually propagating at a speed of 2,782.5 m/s.

It is more accurate to say that, in the simulation, interference produced a wave packet whose peak corresponded to this apparent speed.

And yet the story itself is unusual: a problem initially concerned with how to hear and locate a whale in the ocean more accurately led the researchers to a fundamental question about what exactly we mean when we talk about the ‘speed’ of a wave.

Source

Study: “Supersonic and superluminal energy and speed of information via temporal interference in a dispersionless environment”.

Authors: John L. Spiesberger, Eugene Terray — University of Pennsylvania and Woods Hole Oceanographic Institution.

Journal: Physical Review E, Volume 114, Article 025107. The paper was published on 18 August 2026.