The Rijke tube is a cylindrical tube with both ends open, inside of which a heat source is placed that turns

heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...

into

sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

, by creating a self-amplifying

standing wave In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect ...

. It is an entertaining phenomenon in

acoustics Acoustics is a branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician ...

and is an excellent example of

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

Discovery

P. L. Rijke was a

professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who pr ...

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

at the

Leiden University Leiden University (abbreviated as ''LEI''; nl, Universiteit Leiden) is a Public university, public research university in Leiden, Netherlands. The university was founded as a Protestant university in 1575 by William the Silent, William, Prince o ...

in the

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

when, in 1859, he discovered a way of using heat to sustain a sound in a

cylindrical A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infini ...

tube open at both ends. He used a

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...

tube, about 0.8 m long and 3.5 cm in diameter. Inside it, about 20 cm from one end, he placed a disc of

wire gauze A wire gauze or wire mesh is a sheet of thin metal that has net-like patterns. Wire gauze is placed on the support ring that is attached to the retort stand between the Bunsen burner and glassware or is placed on a tripod to support the beakers, ...

as shown in the figure on right.

Friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of t ...

with the walls of the tube is sufficient to keep the gauze in position. With the tube vertical and the gauze in the lower half, he heated the gauze with a

flame A flame (from Latin ''flamma'') is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density they ...

until it was glowing red hot. Upon removing the flame, he obtained a loud sound from the tube which lasted until the gauze cooled down (about 10 s). It is safer in modern reproductions of this experiment to use a

borosilicate glass Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...

tube or, better still, one made of

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

. Instead of heating the gauze with a flame, Rijke also tried

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...

heating. Making the gauze with electrical

resistance wire Resistance wire is wire intended for making electrical resistors (which are used to control the amount of current in a circuit). It is better if the alloy used has a high resistivity, since a shorter wire can then be used. In many situations, the ...

causes it to glow red when a sufficiently large

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

is passed. With the heat being continuously supplied, the sound is also continuous and rather loud. Rijke seems to have received complaints from his university colleagues because he reports that the sound could be easily heard three rooms away from his laboratory. The electrical power required to achieve this is about 1 kW.

Lord Rayleigh John William Strutt, 3rd Baron Rayleigh, (; 12 November 1842 – 30 June 1919) was an English mathematician and physicist who made extensive contributions to science. He spent all of his academic career at the University of Cambridge. Amo ...

, who wrote the definitive textbook on sound in 1877, recommends this as a very effective

lecture A lecture (from Latin ''lēctūra'' “reading” ) is an oral presentation intended to present information or teach people about a particular subject, for example by a university or college teacher. Lectures are used to convey critical inform ...

demonstration. He used a

cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...

pipe 1.5 m long and 12 cm diameter with two layers of gauze made from

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

wire inserted about quarter of the way up the tube. The extra gauze is to retain more heat, which makes the sound longer lasting. He reports in his book that the sound rises to such intensity as to shake the room! A "reverse" Rijke effect — namely, that a Rijke tube will also produce audio oscillations if ''hot'' air flows through a ''cold'' screen — was first observed by Rijke's assistant Johannes Bosscha and subsequently investigated by German physicist Peter Theophil Rieß.

Mechanism

The sound comes from a

whose

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

is about twice the length of the tube, giving the

fundamental frequency The fundamental frequency, often referred to simply as the ''fundamental'', is defined as the lowest frequency of a periodic waveform. In music, the fundamental is the musical pitch of a note that is perceived as the lowest partial present. In ...

. Lord Rayleigh, in his book, gave the correct explanation of how the sound is stimulated. The flow of air past the gauze is a combination of two motions. There is a uniform upwards motion of the air due to a

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

current resulting from the gauze heating up the air. Superimposed on this is the motion due to the sound wave. For half the vibration cycle, the air flows into the tube from both ends until the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

reaches a maximum. During the other half cycle, the flow of air is outwards until the minimum pressure is reached. All air flowing past the gauze is

ed to the temperature of the gauze and any transfer of heat to the air will increase its pressure according to the ideal gas law. As the air flows upwards past the gauze most of it will already be hot because it has just come downwards past the gauze during the previous half cycle. However, just before the pressure maximum, a small quantity of cool air comes into contact with the gauze and its pressure is suddenly increased. This increases the pressure maximum, so reinforcing the vibration. During the other half cycle, when the pressure is decreasing, the air above the gauze is forced downwards past the gauze again. Since it is already hot, no pressure change due to the gauze takes place, since there is no transfer of heat. The sound wave is therefore reinforced once every vibration cycle, and it quickly builds up to a very large

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplit ...

. This explains why there is no sound when the flame is heating the gauze: all air flowing through the tube is heated by the flame, so when it reaches the gauze, it is already hot and no pressure increase takes place. When the gauze is in the upper half of the tube, there is no sound. In this case, the cool air brought in from the bottom by the convection current reaches the gauze towards the end of the outward vibration movement. This is immediately before the pressure minimum, so a sudden increase in pressure due to the heat transfer tends to cancel out the sound wave instead of reinforcing it. The position of the gauze in the tube is not critical as long as it is in the lower half. To work out its best position, there are two things to consider. Most heat will be transferred to the air where the displacement of the wave is a maximum, i.e. at the end of the tube. However, the effect of increasing the pressure is greatest where there is the greatest pressure variation, i.e. in the middle of the tube. Placing the gauze midway between these two positions (one quarter of the way in from the bottom end) is a simple way to come close to the optimal placement. The Rijke tube is considered to be a standing wave form of thermoacoustic devices known as "

heat engine In thermodynamics and engineering, a heat engine is a system that converts heat to mechanical energy, which can then be used to do mechanical work. It does this by bringing a working substance from a higher state temperature to a lower state ...

s" or " prime movers".

Sondhauss tube

The Rijke tube operates with both ends open. However, a tube with one end closed will also generate sound from heat, if the closed end is very hot. Such a device is called a “Sondhauss tube”. The phenomenon was first observed by glassblowers and was first described in 1850 by the German physicist Karl Friedrich Julius Sondhauss (1815–1886). Lord Rayleigh first explained the operation of the Sondhauss tube. The Sondhauss tube operates in a way that is basically similar to the Rijke tube: Initially, air moves towards the hot, closed end of the tube, where it's heated, so that the pressure at that end increases. The hot, higher-pressure air then flows from the closed end towards the cooler, open end of the tube. The air transfers its heat to the tube and cools. The air surges slightly beyond the open end of the tube, briefly compressing the atmosphere; the compression propagates through the atmosphere as a sound wave. The atmosphere then pushes the air back into the tube, and the cycle repeats. Unlike the Rijke tube, the Sondhauss tube does not require a steady flow of air through it, and whereas the Rijke tube acts as a half-wave resonator, the Sondhauss tube acts as a quarter-wave resonator. Like the Rijke tube, it was discovered that placing a porous heater — as well as a "stack" (a "plug" that is porous) — in the tube greatly increased the power and efficiency of the Sondhauss tube. (In demonstration models, the tube can be heated externally and steel wool can serve as a stack.)On YouTube, see for example:
"Resonant Stirling"

"Laser de sonido thermoacoustic sound saser"
or
"thermoacoustic experiment"

References

Further information

*
''Rijke-Rohr'' (Rijke tube) at: ''Wundersames Sammelsurium'' (Wondrous Collection)
(in German) Includes original articles by early investigators of thermoacoustics (Rijke, Reiss, etc.). * * Julius Sumner Miller
"Sounding Pipes" on YouTube
Demonstrations of Rijke tubes. {{DEFAULTSORT:Rijke Tube Acoustics Hot air engines Plasmaphones Toy instruments and noisemakers

Discovery

Mechanism

Sondhauss tube

See also

References

Further information