Aerodynamic Noise produced by a Gliding Owl

Gruschka, H. D.; Borchers, I. U.; Coble, Jamie B.

doi:10.1038/233409a0

Cited by 47 publications

(24 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thorpe and Griffin 38 additionally noticed the lack of ultrasonic components in the flapping flight noise of owls. One of the most detailed studies regarding the silent owl flight was done by Kroeger et al 21 and by Gruschka et al, 16 where the aim was to use the knowledge of the quieting mechanisms of the owl for the development of future quiet aircraft. They conducted flyover measurements on a Florida barred owl (Strix varia alleni ) during the phase of gliding flight in a reverberation chamber using a single condenser microphone.…”

Section: Ib the Silent Flight Of Owlsmentioning

confidence: 99%

Silent Owl Flight: Acoustic Wind Tunnel Measurements on Prepared Wings

Geyer

Sarradj

Fritzsche

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

View full text Add to dashboard Cite

The wings and feathers of most genera of owls show unique properties that are held responsible for the silent flight of the owls. This ability to fly silently has long been of interest for engineers, with the aim to transfer the basic noise reducing mechanisms to technical applications such as blades of fans and propellers. The present paper describes acoustic and aerodynamic wind tunnel measurements on prepared bird wings of different species, among them two silently flying species of owls, the barn owl (Tyto alba) and the tawny owl (Strix aluco). The different wings are characterized in the study as technical airfoils in terms of their acoustic and aerodynamic performance. The experiments took place in an aeroacoustic open jet wind tunnel using microphone array measurement technique and deconvolution beamforming algorithms. Simultaneously to the acoustic measurements, the lift and drag forces of the wings were captured using a six-component-balance. This study, which is a complementary study to the approach of performing flyover measurements on flying birds, further confirms experimentally that the silent owl flight is a consequence of the special wing and plumage adaptations of the owls and not a consequence of their lower flight speed only.

show abstract

Section: Ib the Silent Flight Of Owlsmentioning

confidence: 99%

Silent Owl Flight: Acoustic Wind Tunnel Measurements on Prepared Wings

Geyer

Sarradj

Fritzsche

2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

View full text Add to dashboard Cite

show abstract

“…Thorpe and Griffin [6] additionally noticed the lack of ultrasonic components in the flapping flight noise of owls. One of the most detailed studies regarding the silent owlfl ight wasd one in 1971 by Kroeger et al [7] and by Gruschka et al [8], where the aim wast ou se the knowledge of the quieting mechanisms of the owlf or the development of future quiet aircraft. Theyconducted flyovermeasurements on a Florida barred owl( Strix varia alleni)d uring the phase of gliding flight in ar everberation chamber using as ingle condenser microphone.…”

Section: The Silent Flight Of Owlsmentioning

confidence: 99%

Silent Owl Flight: Comparative Acoustic Wind Tunnel Measurements on Prepared Wings

Geyer¹,

Sarradj²,

Fritzsche³

2013

Acta Acustica united with Acustica

View full text Add to dashboard Cite

The wings and feathers of most genera of owls showu nique properties that are held responsible for the silent flight of the owls. This ability to fly silently has long been of interest for engineers, with the aim to transfer the basic noise reducing mechanisms to technical applications such as blades of fans and propellers. The present paper describes acoustic and aerodynamic wind tunnel measurements on prepared bird wings of different species, among them twosilently flying species of owls, the barn owl( Tyto alba)a nd the tawnyo wl (Strix aluco). The different wings are characterized in the study as technical airfoils in terms of their acoustic and aerodynamic performance. The experiments took place in an aeroacoustic open jet wind tunnel using microphone array measurement technique and deconvolution beamforming algorithms. Simultaneously to the acoustic measurements, the aerodynamic forces of the wings were captured using asix-component balance. This study,which is acomplementary study to the approach of performing flyoverm easurements on birds flying in gliding flight, further confirms experimentally that the silent owlflight is aconsequence of the special wing and plumage adaptations of the owls and not aconsequence of their lower flight speed only.

show abstract

“…Gruschka et al [18] studied the noise production of a gliding barred owl (Strix varia). These authors observed sound pressure levels that were inaudible to humans at 3 m distance and further away.…”

Section: Early Observationsmentioning

confidence: 99%

Features of owl wings that promote silent flight

et al. 2017

View full text Add to dashboard Cite

Owls are an order of birds of prey that are known for the development of a silent flight. We review here the morphological adaptations of owls leading to silent flight and discuss also aerodynamic properties of owl wings. We start with early observations (until 2005), and then turn to recent advances. The large wings of these birds, resulting in low wing loading and a low aspect ratio, contribute to noise reduction by allowing slow flight. The serrations on the leading edge of the wing and the velvet-like surface have an effect on noise reduction and also lead to an improvement of aerodynamic performance. The fringes at the inner feather vanes reduce noise by gliding into the grooves at the lower wing surface that are formed by barb shafts. The fringed trailing edge of the wing has been shown to reduce trailing edge noise. These adaptations to silent flight have been an inspiration for biologists and engineers for the development of devices with reduced noise production. Today several biomimetic applications such as a serrated pantograph or a fringed ventilator are available. Finally, we discuss unresolved questions and possible future directions.

show abstract

Aerodynamic Noise produced by a Gliding Owl

Cited by 47 publications

References 1 publication

Silent Owl Flight: Acoustic Wind Tunnel Measurements on Prepared Wings

Silent Owl Flight: Acoustic Wind Tunnel Measurements on Prepared Wings

Silent Owl Flight: Comparative Acoustic Wind Tunnel Measurements on Prepared Wings

Features of owl wings that promote silent flight

Contact Info

Product

Resources

About