### Abstract

Original language | English |
---|---|

Title of host publication | Proceeding of the 20th International Congress on Sound and Vibration 2013 |

Editors | Malcolm J. Crocker, Marek Pawelczyk, Boonchoat Paosawatyanyong |

Publisher | International Institute of Acoustics and Vibration IIAV |

Pages | 2553-2559 |

Volume | 3 |

ISBN (Print) | 978-1-62993-150-0 |

Publication status | Published - 2013 |

MoE publication type | A4 Article in a conference publication |

Event | 20th International Congress on Sound and Vibration - Bangkok, Thailand Duration: 7 Jul 2013 → 11 Jul 2013 |

### Conference

Conference | 20th International Congress on Sound and Vibration |
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Abbreviated title | ICSV 20 |

Country | Thailand |

City | Bangkok |

Period | 7/07/13 → 11/07/13 |

### Fingerprint

### Keywords

- high frequency range
- in-duct sound power
- acoustic source characteristics

### Cite this

*Proceeding of the 20th International Congress on Sound and Vibration 2013*(Vol. 3, pp. 2553-2559). International Institute of Acoustics and Vibration IIAV.

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*Proceeding of the 20th International Congress on Sound and Vibration 2013.*vol. 3, International Institute of Acoustics and Vibration IIAV, pp. 2553-2559, 20th International Congress on Sound and Vibration, Bangkok, Thailand, 7/07/13.

**Estimating the high frequency in-duct sound power using sound pressures at the duct wall.** / Hynninen, Antti; Åbom, M.

Research output: Chapter in Book/Report/Conference proceeding › Conference article in proceedings › Scientific › peer-review

TY - GEN

T1 - Estimating the high frequency in-duct sound power using sound pressures at the duct wall

AU - Hynninen, Antti

AU - Åbom, M.

N1 - Project: 82112

PY - 2013

Y1 - 2013

N2 - When studying the acoustic wave propagation in a channel, the frequency range can be divided to the low frequency plane wave range and to the high frequency range with non-plane waves. In the low frequency range the wave propagation is one-dimensional and the governing equations are rather simple. The larger the duct the lower the frequency limit of the non-plane waves. Therefore taking into account also the three-dimensional acoustic wave propagation is important especially when considering the duct systems used in large structures, e.g., medium speed internal combustion engines (IC-engines), fans, or compressors. Harsh environment and unmovable structures restrict the use of standardized noise measuring methods. To characterize the medium speed IC-engine exhaust noise in situ, the in-duct sound pressures are measured using wall mounted transducers. Then the source sound power is estimated from the propagating sound pressures, which is the power based approach. The power based approach is only valid in frequency averaged sense and therefore the source power must be defined in one-third octave frequency bands, for example. One way to estimate the source sound power in the high frequency range, is to extend the classical plane wave formulation by defining the one-third octave frequency band weighting factors for different excitation types. The aim of this study is to define these weighting factors using finite element method (FEM) simulations of a test duct with non-reflecting terminations. The sound pressures at the duct wall were compared to the sound pressures at the duct end for randomized multi-modal excitations. From statistics, the one-third octave band weighting factors and their reliability were estimated.

AB - When studying the acoustic wave propagation in a channel, the frequency range can be divided to the low frequency plane wave range and to the high frequency range with non-plane waves. In the low frequency range the wave propagation is one-dimensional and the governing equations are rather simple. The larger the duct the lower the frequency limit of the non-plane waves. Therefore taking into account also the three-dimensional acoustic wave propagation is important especially when considering the duct systems used in large structures, e.g., medium speed internal combustion engines (IC-engines), fans, or compressors. Harsh environment and unmovable structures restrict the use of standardized noise measuring methods. To characterize the medium speed IC-engine exhaust noise in situ, the in-duct sound pressures are measured using wall mounted transducers. Then the source sound power is estimated from the propagating sound pressures, which is the power based approach. The power based approach is only valid in frequency averaged sense and therefore the source power must be defined in one-third octave frequency bands, for example. One way to estimate the source sound power in the high frequency range, is to extend the classical plane wave formulation by defining the one-third octave frequency band weighting factors for different excitation types. The aim of this study is to define these weighting factors using finite element method (FEM) simulations of a test duct with non-reflecting terminations. The sound pressures at the duct wall were compared to the sound pressures at the duct end for randomized multi-modal excitations. From statistics, the one-third octave band weighting factors and their reliability were estimated.

KW - high frequency range

KW - in-duct sound power

KW - acoustic source characteristics

M3 - Conference article in proceedings

SN - 978-1-62993-150-0

VL - 3

SP - 2553

EP - 2559

BT - Proceeding of the 20th International Congress on Sound and Vibration 2013

A2 - Crocker, Malcolm J.

A2 - Pawelczyk, Marek

A2 - Paosawatyanyong, Boonchoat

PB - International Institute of Acoustics and Vibration IIAV

ER -