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edit approved Jul 24, 2022 at 9:06
Glorfindel
edit approved Jul 24, 2022 at 9:06
Glorfindel
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Short Answer:

The sound is caused by airflow across holes on the underside of the wings of certain aircraft.

Long Answer:

I too have noted the sound phenomenon that you describe. This videoThis video has a great example between 0:26-52 (link starts playback at 0:26 where the noise starts):

I will readily admit that this answer is mostly just a compilation of what I have learned researching this. Your question intrigued me and I've enjoyed learning about it!

As I discovered as I started researching this, many others are familiar with the noise as well. This article on Airliners.net had a lot of discussion about it, starting with a lot of interesting—but ultimately flawed—theories.

But, that thread led me to the answer to your question, which is: the sound is caused by the "circular opening used to equalise the pressure in wing fuel tanks", according to Euractiv.comEuractiv.com

This article on AirportWatchThis article on AirportWatch further explains:

The Airbus 320 series of aircraft, [...] have been known for many years [...] to have a particularly irritating high pitched whine. This is caused by air rushing across the under-surface of the wing, where there are Fuel Over Pressure Protector (FOPP) cavities. This generates noise, in the same way as blowing air over the mouth of a bottle. Every A320 series aircraft emits a signature howling noise while approaching to land. It is heard most when the plane is travelling at around 160 knots, and the frequency is around 500-600Hz, which is close to peak sensitivity of the human ear.

That being said, there is apparently a fix to that problem, as both the aforementioned links describe. As Euractiv.comEuractiv.com explains, the fix is a vortex generator:

a 5-cm triangular piece of aluminium sheet metal upstream of the two vents on each wing, in order to divert the air flow and stop the whistle. A decade of research went into the vortex generator, which stems from efforts to mask a similar whistle produced when air blows over the gun ports of warplanes.

This image shows both the FOPP hole, and the VG that softens the sound:

A320 FOPP and VGImage Courtesy of Lufthansa[Image Courtesy of Lufthansa]

Read the articles linked, interesting stuff therein!

Short Answer:

The sound is caused by airflow across holes on the underside of the wings of certain aircraft.

Long Answer:

I too have noted the sound phenomenon that you describe. This video has a great example between 0:26-52 (link starts playback at 0:26 where the noise starts):

I will readily admit that this answer is mostly just a compilation of what I have learned researching this. Your question intrigued me and I've enjoyed learning about it!

As I discovered as I started researching this, many others are familiar with the noise as well. This article on Airliners.net had a lot of discussion about it, starting with a lot of interesting—but ultimately flawed—theories.

But, that thread led me to the answer to your question, which is: the sound is caused by the "circular opening used to equalise the pressure in wing fuel tanks", according to Euractiv.com

This article on AirportWatch further explains:

The Airbus 320 series of aircraft, [...] have been known for many years [...] to have a particularly irritating high pitched whine. This is caused by air rushing across the under-surface of the wing, where there are Fuel Over Pressure Protector (FOPP) cavities. This generates noise, in the same way as blowing air over the mouth of a bottle. Every A320 series aircraft emits a signature howling noise while approaching to land. It is heard most when the plane is travelling at around 160 knots, and the frequency is around 500-600Hz, which is close to peak sensitivity of the human ear.

That being said, there is apparently a fix to that problem, as both the aforementioned links describe. As Euractiv.com explains, the fix is a vortex generator:

a 5-cm triangular piece of aluminium sheet metal upstream of the two vents on each wing, in order to divert the air flow and stop the whistle. A decade of research went into the vortex generator, which stems from efforts to mask a similar whistle produced when air blows over the gun ports of warplanes.

This image shows both the FOPP hole, and the VG that softens the sound:

A320 FOPP and VGImage Courtesy of Lufthansa[Image Courtesy of Lufthansa]

Read the articles linked, interesting stuff therein!

Short Answer:

The sound is caused by airflow across holes on the underside of the wings of certain aircraft.

Long Answer:

I too have noted the sound phenomenon that you describe. This video has a great example between 0:26-52 (link starts playback at 0:26 where the noise starts):

I will readily admit that this answer is mostly just a compilation of what I have learned researching this. Your question intrigued me and I've enjoyed learning about it!

As I discovered as I started researching this, many others are familiar with the noise as well. This article on Airliners.net had a lot of discussion about it, starting with a lot of interesting—but ultimately flawed—theories.

But, that thread led me to the answer to your question, which is: the sound is caused by the "circular opening used to equalise the pressure in wing fuel tanks", according to Euractiv.com

This article on AirportWatch further explains:

The Airbus 320 series of aircraft, [...] have been known for many years [...] to have a particularly irritating high pitched whine. This is caused by air rushing across the under-surface of the wing, where there are Fuel Over Pressure Protector (FOPP) cavities. This generates noise, in the same way as blowing air over the mouth of a bottle. Every A320 series aircraft emits a signature howling noise while approaching to land. It is heard most when the plane is travelling at around 160 knots, and the frequency is around 500-600Hz, which is close to peak sensitivity of the human ear.

That being said, there is apparently a fix to that problem, as both the aforementioned links describe. As Euractiv.com explains, the fix is a vortex generator:

a 5-cm triangular piece of aluminium sheet metal upstream of the two vents on each wing, in order to divert the air flow and stop the whistle. A decade of research went into the vortex generator, which stems from efforts to mask a similar whistle produced when air blows over the gun ports of warplanes.

This image shows both the FOPP hole, and the VG that softens the sound:

A320 FOPP and VGImage Courtesy of Lufthansa[Image Courtesy of Lufthansa]

Read the articles linked, interesting stuff therein!

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J W
J W
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Short Answer:

The sound is caused by airflow across holes on the underside of the wings of certain aircraft.

Long Answer:

I too have noted the sound phenomenon that you describe. This video has a great example between 0:26-52 (link starts playback at 0:26 where the noise starts).

:

I will readily admit that this answer is mostly just a compilation of what I have learned researching this. Your question intrigued me and I've enjoyed learning about it!

As I discovered as I started researching this, many others are familiar with the noise as well. This article on Airliners.net had a lot of discussion about it, starting with a lot of interesting—but ultimately flawed—theories.

But, that thread led me to the answer to your question, which is: the sound is caused by the "circular opening used to equalise the pressure in wing fuel tanks", according to Euractiv.com

This article on AirportWatch further explains:

The Airbus 320 series of aircraft, [...] have been known for many years [...] to have a particularly irritating high pitched whine. This is caused by air rushing across the under-surface of the wing, where there are Fuel Over Pressure Protector (FOPP) cavities. This generates noise, in the same way as blowing air over the mouth of a bottle. Every A320 series aircraft emits a signature howling noise while approaching to land. It is heard most when the plane is travelling at around 160 knots, and the frequency is around 500-600Hz, which is close to peak sensitivity of the human ear.

That being said, there is apparently a fix to that problem, as both the aforementioned links describe. As Euractiv.com explains, the fix is a vortex generator:

a 5-cm triangular piece of aluminium sheet metal upstream of the two vents on each wing, in order to divert the air flow and stop the whistle. A decade of research went into the vortex generator, which stems from efforts to mask a similar whistle produced when air blows over the gun ports of warplanes.

This image shows both the FOPP hole, and the VG that softens the sound:

A320 FOPP and VGImage Courtesy of Lufthansa[Image Courtesy of Lufthansa]

Read the articles linked, interesting stuff therein!

Short Answer:

The sound is caused by airflow across holes on the underside of the wings of certain aircraft.

Long Answer:

I too have noted the sound phenomenon that you describe. This video has a great example between 0:26-52 (link starts playback at 0:26 where the noise starts).

I will readily admit that this answer is mostly just a compilation of what I have learned researching this. Your question intrigued me and I've enjoyed learning about it!

As I discovered as I started researching this, many others are familiar with the noise as well. This article on Airliners.net had a lot of discussion about it, starting with a lot of interesting—but ultimately flawed—theories.

But, that thread led me to the answer to your question, which is: the sound is caused by the "circular opening used to equalise the pressure in wing fuel tanks", according to Euractiv.com

This article on AirportWatch further explains:

The Airbus 320 series of aircraft, [...] have been known for many years [...] to have a particularly irritating high pitched whine. This is caused by air rushing across the under-surface of the wing, where there are Fuel Over Pressure Protector (FOPP) cavities. This generates noise, in the same way as blowing air over the mouth of a bottle. Every A320 series aircraft emits a signature howling noise while approaching to land. It is heard most when the plane is travelling at around 160 knots, and the frequency is around 500-600Hz, which is close to peak sensitivity of the human ear.

That being said, there is apparently a fix to that problem, as both the aforementioned links describe. As Euractiv.com explains, the fix is a vortex generator:

a 5-cm triangular piece of aluminium sheet metal upstream of the two vents on each wing, in order to divert the air flow and stop the whistle. A decade of research went into the vortex generator, which stems from efforts to mask a similar whistle produced when air blows over the gun ports of warplanes.

This image shows both the FOPP hole, and the VG that softens the sound:

A320 FOPP and VGImage Courtesy of Lufthansa[Image Courtesy of Lufthansa]

Read the articles linked, interesting stuff therein!

Short Answer:

The sound is caused by airflow across holes on the underside of the wings of certain aircraft.

Long Answer:

I too have noted the sound phenomenon that you describe. This video has a great example between 0:26-52 (link starts playback at 0:26 where the noise starts):

I will readily admit that this answer is mostly just a compilation of what I have learned researching this. Your question intrigued me and I've enjoyed learning about it!

As I discovered as I started researching this, many others are familiar with the noise as well. This article on Airliners.net had a lot of discussion about it, starting with a lot of interesting—but ultimately flawed—theories.

But, that thread led me to the answer to your question, which is: the sound is caused by the "circular opening used to equalise the pressure in wing fuel tanks", according to Euractiv.com

This article on AirportWatch further explains:

The Airbus 320 series of aircraft, [...] have been known for many years [...] to have a particularly irritating high pitched whine. This is caused by air rushing across the under-surface of the wing, where there are Fuel Over Pressure Protector (FOPP) cavities. This generates noise, in the same way as blowing air over the mouth of a bottle. Every A320 series aircraft emits a signature howling noise while approaching to land. It is heard most when the plane is travelling at around 160 knots, and the frequency is around 500-600Hz, which is close to peak sensitivity of the human ear.

That being said, there is apparently a fix to that problem, as both the aforementioned links describe. As Euractiv.com explains, the fix is a vortex generator:

a 5-cm triangular piece of aluminium sheet metal upstream of the two vents on each wing, in order to divert the air flow and stop the whistle. A decade of research went into the vortex generator, which stems from efforts to mask a similar whistle produced when air blows over the gun ports of warplanes.

This image shows both the FOPP hole, and the VG that softens the sound:

A320 FOPP and VGImage Courtesy of Lufthansa[Image Courtesy of Lufthansa]

Read the articles linked, interesting stuff therein!

Source Link
J W
J W
  • 16.6k
  • 3
  • 60
  • 115

Short Answer:

The sound is caused by airflow across holes on the underside of the wings of certain aircraft.

Long Answer:

I too have noted the sound phenomenon that you describe. This video has a great example between 0:26-52 (link starts playback at 0:26 where the noise starts).

I will readily admit that this answer is mostly just a compilation of what I have learned researching this. Your question intrigued me and I've enjoyed learning about it!

As I discovered as I started researching this, many others are familiar with the noise as well. This article on Airliners.net had a lot of discussion about it, starting with a lot of interesting—but ultimately flawed—theories.

But, that thread led me to the answer to your question, which is: the sound is caused by the "circular opening used to equalise the pressure in wing fuel tanks", according to Euractiv.com

This article on AirportWatch further explains:

The Airbus 320 series of aircraft, [...] have been known for many years [...] to have a particularly irritating high pitched whine. This is caused by air rushing across the under-surface of the wing, where there are Fuel Over Pressure Protector (FOPP) cavities. This generates noise, in the same way as blowing air over the mouth of a bottle. Every A320 series aircraft emits a signature howling noise while approaching to land. It is heard most when the plane is travelling at around 160 knots, and the frequency is around 500-600Hz, which is close to peak sensitivity of the human ear.

That being said, there is apparently a fix to that problem, as both the aforementioned links describe. As Euractiv.com explains, the fix is a vortex generator:

a 5-cm triangular piece of aluminium sheet metal upstream of the two vents on each wing, in order to divert the air flow and stop the whistle. A decade of research went into the vortex generator, which stems from efforts to mask a similar whistle produced when air blows over the gun ports of warplanes.

This image shows both the FOPP hole, and the VG that softens the sound:

A320 FOPP and VGImage Courtesy of Lufthansa[Image Courtesy of Lufthansa]

Read the articles linked, interesting stuff therein!