Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa).
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👉 Acoustic pressure in the context of 1883 eruption of Krakatoa
Between 20 May and 21 October 1883, the volcanic island of Krakatau, located in the Sunda Strait, erupted. On 27 August, the island had its most significant eruption, which destroyed over 70% of the island and its surrounding archipelago, afterwards collapsing itself into a caldera. The 27 August eruption had an estimated Volcanic Explosivity Index (VEI) of 6, and is one of the deadliest and most destructive volcanic events in recorded history; the third explosion of that day, which occurred at 10:02 am, remains the loudest known sound in history.
The explosion was heard 3,110 kilometres (1,930 mi) away in Perth, Western Australia, and Rodrigues near Mauritius, 4,800 kilometres (3,000 mi) away. The acoustic pressure wave circled the globe more than three times. At least 36,417 deaths are attributed to the eruption and the tsunamis it created. Significant additional effects were felt worldwide in the days and weeks after the volcano's eruption. Additional seismic activity was reported until February 1884, but any reports after October 1883 were dismissed by Rogier Verbeek's subsequent investigation into the eruption.
In this Dossier
Acoustic pressure in the context of Acoustic wave
Acoustic waves are types of waves that propagate through matter—such as gas, liquid, and/or solids—by causing the particles of the medium to compress and expand. These waves carry energy and are characterized by properties like acoustic pressure, particle velocity, and acoustic intensity. The speed of an acoustic wave depends on the properties of the medium it travels through; for example, it travels at approximately 343 meters per second in air, and 1480 meters per second in water. Acoustic waves encompass a broad range of phenomena, from audible sound to seismic waves and ultrasound, finding applications in diverse fields like acoustics, engineering, and medicine.
Acoustic pressure in the context of Acoustic impedance
Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting from an acoustic pressure applied to the system. The SI unit of acoustic impedance is the pascal-second per cubic metre (symbol Pa·s/m), or in the MKS system the rayl per square metre (Rayl/m), while that of specific acoustic impedance is the pascal-second per metre (Pa·s/m), or in the MKS system the rayl (Rayl). There is a close analogy with electrical impedance, which measures the opposition that a system presents to the electric current resulting from a voltage applied to the system.