# Derivation of Lighthill’s Eighth Power Law of an Aeroacoustic Quadrupole in Acoustic Spacetime

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## Abstract

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## 1. Introduction

- physical mechanism of sound generation by pure instability in a fluid (in contrast to moving solid bodies or boundaries, which involve forces external to the fluid),
- quadrupole sound radiation in free space,
- inefficiency of kinetic-to-acoustic energy conversion in the flow of fluid, and
- power scaling for an aeroacoustic quadrupole source, which Lighthill was able to derive even without an accurate description of the flow, and its relation with the other two main types of sources—monopole and dipole.

## 2. Waves and Motion in Acoustic Spacetime

## 3. Aeroacoustic Sound Generation

## 4. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**MDPI and ACS Style**

Masovic, D.; Sarradj, E.
Derivation of Lighthill’s Eighth Power Law of an Aeroacoustic Quadrupole in Acoustic Spacetime. *Acoustics* **2020**, *2*, 666-673.
https://doi.org/10.3390/acoustics2030035

**AMA Style**

Masovic D, Sarradj E.
Derivation of Lighthill’s Eighth Power Law of an Aeroacoustic Quadrupole in Acoustic Spacetime. *Acoustics*. 2020; 2(3):666-673.
https://doi.org/10.3390/acoustics2030035

**Chicago/Turabian Style**

Masovic, Drasko, and Ennes Sarradj.
2020. "Derivation of Lighthill’s Eighth Power Law of an Aeroacoustic Quadrupole in Acoustic Spacetime" *Acoustics* 2, no. 3: 666-673.
https://doi.org/10.3390/acoustics2030035