Revival of the particle concept of Sound

Abstract

           There are two schools of thought for the concept of sound as revealed from history. According to one concept, sound is caused by release of tiny subatomic particles from matter; propagation of particles through a medium and interaction with other existences at a distance such as the ear of living beings. The second accepted sound is caused by vibration of a source communicated by waves in a medium and capable of affecting any existence at a distance. The above hypotheses stand on different footings which cannot be harmonized to develop a single theory for sound. The reality being one, only one concept of sound is real. The wave concept of sound is well accepted leaving behind the particle concept. At times, reality is suppressed if it is not promoted properly. It is something like an honest client sometimes loses the case due to the weak argument of his pleader. Now phonons (particles) are conceptualized as the quantized units of vibrational energy in solids. The phonons are formally integrated into solid-state physics, describing sound as a quantum mechanical phenomenon in materials. Thus, both particle concept and the wave concept are accepted allowing the dual concept for sound. This author has shown that mechanical waves of sound frequency produced in air by oscillation of a plunger/piston does not produce sound which straight away disagrees with the wave concept of sound. Hence, the particle concept of sound needs to be augmented by realizing additional qualities in sound particles in the light of reality so that the particle theory alone can justify 1) why sound is not heard from outside the ringing bell in vacuum jar and 2) how different phenomena of sound including diffraction and interference can be explained from the particle concept of sound. Quantum Acoustics and the interpretation of solid-state physics on sound conceptualizes hypothetical sound particles as phonons. Thus, the particle concept is inevitable in advance analysis of sound in solid state. If sound particles have natural existence in the structure of solid then it is rational to conceptualize the same instead of formalizing the hypothetical phonon. It is further necessary to identify new qualities of sound particles for understanding interference and diffraction thereby dispensing the duality. The new concept of sound particles as envisaged here carries fractional charge. This paper shows how the sound-wave concept is far from reality and explains why the sound particles produced in vacuum cannot cross the wall of the vacuum chamber. The new particle theory of sound has scope of explaining the diffraction & interference phenomenon of sound and is in harmony with solid state physics.

Key Words: Particle concept of sound, Wave concept of sound, Phonons, Vibrational energy, diffraction, interference, Solid state physics, Quantum Acoustics.

Historical development on concept of sound

• Pythagoras in 6th century BCE associated sound with the movement of objects but did not formalize a particle-based model.
• Democritus in 5th century BCE speculated that all matter, including sound, could consist of tiny particles, hinting at a particulate understanding of various phenomena. 
• Aristotle in 4th century BCE correctly suggested that a sound wave propagates in air through motion of the air. 
• Lucretius in the 1st century BCE described sound as being made up of small, fast-moving particles that interact with air and the ear.
• Vitruvius, in 1st century BCE determined the mechanism of transmission of sound waves.
• Boethius in 6th century AD suggested that the human perception of pitch is related to the physical property of frequency. 
• Marin Mersenne in 1637 studied the vibration of stretched strings; the results of these studies were summarized in the three Mersenne’s laws.
• Galileo Galilei in 1638 identified the role of frequency in determining pitch.
• Pierre Gassendi in the 17th century theorized that sound was transmitted through air via particle impacts, akin to billiard balls colliding.
• René Descartes in 1644 proposed that sound involved the motion of tiny particles in the air. 
• Athanasius Kircher in 1650 made the first bell-in-vacuum experiment and showed sound is not through motion of particles.
• Robert Boyle in 1660 demonstrated that sound requires a medium (air) to travel, confirmed that it is not transmitted in a vacuum.
• Marin Mersenne in 1665 calculated the speed of sound in air, marking the first quantitative analysis of sound waves.
• Christiaan Huygens in 1678 proposed the wave theory of light, indirectly influencing later scientists to consider sound as a wave phenomenon.
• Robert Hooke in 1681 first produced a sound wave of known frequency, using a rotating cog wheel as a measuring device.
• Isaac Newton in 1687 suggested that sound travels as a series of compressions and rarefactions in air but also modeled sound propagation mathematically similar to particle motion.
• Isaac Newton in the 1700s attempted to calculate the speed of sound in air using his laws of mechanics, he supported the idea of sound as a pressure wave.
• Daniel Bernoulli in 1738 explored the idea that sound could result from the motion of air particles in a fluid-like model.
• Jean-Baptiste le Rond d’Alembert in 1747 derived the wave equation, providing a mathematical description of sound waves.
• George Stokes in 1827 refined the understanding of wave propagation in fluids and gases, improving the accuracy of sound speed calculation. 
• Hermann von Helmholtz in the 1850s explored the physics of sound and its perception, introducing resonance and analyzed the harmonics of vibrating systems.

Rejection of the Particle Theory and Acceptance of wave theory

The particle theory of sound was rejected due to several reasons:

1. Interference and Diffraction phenomenon of sound is incompatible with particle motion.
2. Sound reflects and refracts predictably, better explained by wave propagation rather than discrete particles. 
3. Particle theory could not explain why sound requires a medium (air, water, solids) for propagation.
4. Euler and Bernoulli developed mathematical models treating sound as pressure variations in air, matching experimental data more accurately.
5. The development of the wave equation provided a comprehensive framework for predicting sound behaviour.
6. Experiments of Thomas Young and Augustin-Jean Fresnel demonstrated wave interference patterns, solidifying the wave model.
7. Robert Boyle showed, sound could not travel without air, reinforcing the need for a medium, which is well explained by wave theory.

Today, sound is understood as a mechanical wave involving oscillations of particles in a medium without the transport of particles themselves. 

Further Development on Sound 

          While sound is fundamentally accepted as a mechanical wave propagating through a medium. In quantum context, it is described through phonons, demonstrating particle-like behaviour. The wave-particle duality of sound is accepted in fields such as ultrasonic, nanotechnology, and quantum acoustics. 

Why again the particle model of sound at this stage? 

The observed pictures of an object viewed from different angles using visible light, ultraviolet ray and x-ray are different though the object remains the same for different observations. Thus, one cannot draw a complete conclusion on the reality of the object from any single view even though each view of the object is a reality. We need to integrate all views of the object for the comprehensive understanding of the object. This philosophy is applicable in exploring the reality of any object or event. Looking into the history of sound we notice, there are two schools of thought for the science of sound: one assumes sound as made up of small, fast-moving particles that interact with air & the ear and the other presumes sound as a mechanical wave involving oscillations of particles of air medium. These two concepts of sound are of diverse nature; hence it is not possible to unify the concepts for understanding the reality. We cannot accept both the concepts since duality is not the reality of nature. When we fail to perceive the reality of sound in an unseen domain from one single concept, we introduce additional concepts to somehow understand different aspects (phenomena) of sound. This led us to believe, duality of sound is also a reality of nature. Now the wave-particle dual concept has proliferated in physics of sound, light and electrons in atomic structure and became established beyond doubt. On the other hand, the reality of nature is perceived as unchanging truth (without duality) in macro domain science, Vedic science, Vedanta, puranas and Bhagavat Geeta. Hence, to help achieve success in unification of sciences, the dual concept is required to be reduced to a single feasible concept. Thus, it is either the particle theory of sound or the wave theory sound corresponds to reality leaving the other as purely hypothetical. To ascertain the reality, both particle and wave concepts need to be examined properly. It is absolutely necessary to examine the circumstances in which sound particles are not propagated through vacuum before rejecting the particle theory of sound. Similarly, it is necessary to justify why sound is not produced by reciprocation of a piston in an open-ended cylinder or oscillation of an electromagnetic plunger that produces waves of sound-frequency in air before accepting the wave theory of sound. The author has provided justification as to how the sound particles generated inside vacuum cannot enter the wall of vacuum chamber. On the other hand, it is difficult to explain why sound is not produced by simulating forced waves of sound-frequency in air. Since waves in air do not produce sound, the wave theory of sound is not a reality and it should not be pursued for theoretical analysis of sound. It is no less a mystery as to how the erroneous wave theory of sound is capable of explaining diffraction and interference of sound. This is possible only when the frequency parameter of a hypothetical sound wave goes to proxy some intrinsic property of sound particles. This author has identified the new significance of electric charge where charge appears in matter (particles) in non-equilibrium state of mass-space association relative to that of its surrounding. The new concept of charge [1] allows existence of fractional charges in particles of matter. The frequency of sound waves in reality goes to describe the charge potential state of real sound particles. 

Discussion on particle concept of sound

         Sound particles present in the micro structure of solid (interstices of atoms & molecules and in grain boundary) are relatively loosely bonded with the microstructure. The strength of bonding of sound particles varies depending on the nature of microstructure of solid and the position of sound particles in the microstructure which is a material specific property. If a sound responding solid is hammered then the microstructure as well as the surface of solid would vibrate liberating some sound particles from the structure. The released sound particles would enter the air medium and move through the medium making collisions with atoms and molecules of the air medium thereby developing a distribution pattern of number density of sound particles in the vicinity of the sound source. Depending on the position of a sound receiver in the said vicinity, it receives different extent of sound particles thereby records different loudness of sound. The surface-vibration of solid generates longitudinal waves in the adjacent air medium which die down within a short distance from the source due to the damping property of the air medium.  In any case, the distance of propagation of longitudinal sound waves is much less than the range of sound propagation. The diaphragm of a sound receiver vibrates by the impact of sound particles which in turn form waves in air-medium. The waves at source and at the receiving end make an illusion, as if the waves are travelling right from the source up to the reception point without break. 

        In vacuum medium the mean free path is longer for the sound particles hence sound particles would travel faster due to minimum collision with atoms and molecules of the air medium. Then, why do the sound particles emitted from a ringing bell in vacuum do not come out of the chamber? It implies, some unknown phenomenon prevents the entry of sound particles through the walls of the vacuum chamber. In the absence of the knowledge of this unknown phenomenon, the fact could not be justified. This was the primary reason why scientists developed faith in the wave theory of sound. The unknown phenomenon is discussed below.

          Every matter particle/body has an extra-nuclear space structure surrounding the particle/body due to mass-space attraction [2]. This phenomenon is well revealed in the celestial body system and atomic system [3]. The same phenomenon also holds good for sound particles. The size of the extranuclear space structure of sound particles is a function of both mass of the nucleus and background space density (pressure), similar to the size of a balloon that depends on internal pressure and external pressure. The sound particles released from the electric bell in vacuum have enlarged extranuclear structure much larger than that in atmospheric air. The solid wall of the vacuum chamber has micro-porosity due to interatomic gaps. The extranuclear space structure of sub-micro sound particles in atmospheric air are of small size which is less than the dimension of micro porosity of the solid wall of the vacuum chamber. Hence the sound particles easily pass through the wall of the vacuum chamber when air is not evacuated from the chamber. But when the air of the chamber is evacuated, the size of the extranuclear space structure of sound particles becomes very large, exceeding the dimension of porosity in the solid wall. The sound particles with increased extranuclear space structure cannot pass through the wall of the vacuum chamber. Hence, no sound of a bell is heard from outside the vacuum chamber. Therefore, the sound produced by an electric bell inside the vacuum chamber propagates up to the wall but fails to penetrate the wall. Hence, no sound is heard from outside the chamber. This gives the misconception that sound does not travel through vacuum. 

Sound is not propagated through wave

           All forms of solid have microstructure composed of micro atomic particles. The micro domain particles also have micro-microstructure composed of micro-micro domain particles (light particles) [4] Many subatomic particles below the range of known microparticles and above the range of micro-micro particles (light particles) have placement in interatomic space in the complex structure of solid. Some of these particles fall in the range of sound particles. Depending on the nature of the microstructure and locational sites of sound particles in the micro structure of solid, the bond-strength and charge state of sound particles have different values. 

         If we hammer a bell-metal, the microstructure of bell metal vibrates at different frequencies depending on the impact of the hammer. Due to the structural vibration, the surface of the bell-metal also vibrates. The vibration of the surface of the bell-metal interacts with the air medium in contact with the surface forming waves in the medium. Due to impact of hammer on bell-metal the following dynamic phenomena occurs:

1. The sound particles are released from the structure of the bell-metal and move into the medium.
2. Waves are formed in the air medium by interaction of vibrating surfaces of the solid which are short lived.
3. We hear sound while remaining in the air medium at a distance from the source. 

          One class of thought is that propagation of sound occurs by motion of sound particles through the air medium and interacts with the ear at a distance. The other class of thought is that the wave formed in the medium by the bell metal propagates in the medium and the wave interacts with the ear. The reason why the sound particles produced by the electric bell in the vacuum chamber cannot come out of the chamber has already been discussed. In fact, there is no problem for the motion of sound particles through vacuum medium but faces problems in entering into the wall of the vacuum chamber. To re-establish the reality of sound waves a different experimental setup is designed (Fig.1).