UairFokker From , joined Dec 1969, posts, RR: Posted (6 years 11 months 5 days 12 hours ago) and read 2579 times:
I am aware that the Dash8 Q400, to reduce noise and vibration, has a complex system of computers who meaure the vibrations and make "counter vibrations" that neutralize the original ones, providing a smooth ride.
Now, my question. All this process, doesn´t stresses the airframe? Doesn´t the Q400 need special care for all this extra stress?
Only a qestion it occured to me this afternoon, and supposed you would know and will be happy to answer.
SK A340 From Sweden, joined Mar 2000, 845 posts, RR: 2 Reply 1, posted (6 years 11 months 5 days 8 hours ago) and read 2547 times:
The SAAB 340 and/or 2000 has it as well and my physics professor told us that it has some kind of "speakers" that emits the "counter waves"/"counter sound" approx. at the level of the passenger's ears. If you would crawl down to the floor the noise would be much higher there. I'm sure though that someone can explain this much better.
N231YE From , joined Dec 1969, posts, RR: Reply 2, posted (6 years 11 months 5 days 7 hours ago) and read 2528 times:
Quoting SK A340 (Reply 1): The SAAB 340 and/or 2000 has it as well and my physics professor told us that it has some kind of "speakers" that emits the "counter waves"/"counter sound" approx. at the level of the passenger's ears.
That is similar, if not the same, as Active Noise Reduction technology found in headsets. In these headsets, the system "listens" for noise and then emits inverse sound waves. When the inverse and normal waves meet, they cancel each other out (distructive interference), causing a reduction in noise.
However, I do remember reading that the DHC-8 Q400 had "counter-vibrators" too, and that question is still open.
Strathpeffer From United Kingdom, joined Jan 2007, 79 posts, RR: 0 Reply 5, posted (6 years 11 months 4 days 12 hours ago) and read 2397 times:
I would argue that NVS, which does indeed work on an identical principle to the headphones, reduces the damaging effects of vibration stress on the airframe because the the 'mirror' vibrations created by the dampers cancel out the original ones from the engines and props.
Think about it this way:
Listening to headphones loud harms your hearing. If your anticipated outcome re. NVS is true then we would predict noise cancelling headphones caused even more harm. This is not the case at all - the overall result is significantly reduced noise NOT more noise added and as a result of eliminating the background you can reduce the chance of damaging your eardrums by setting your music to a lower volume.
As an aside, on a FlyBE Q400 trip from ABZ to BHD a year or so ago the system must have been inoperative because the noise and vibration was staggering. I have always thought these birds are very pleasant on short hops around the UK - but this is certainly not so when NVS is off.
However A Q400 with NVS off is still much better than Logi's Saabs...
Jcs17 From United States of America, joined Jun 2001, 8065 posts, RR: 41 Reply 6, posted (6 years 10 months 4 weeks 1 day 15 hours ago) and read 2209 times:
I was on a USAirways Express Dash 8-200 (non Q-series) a couple of weeks ago. Once in flight, I put my noise-cancelling headphones on to listen to my iPod, and I got significant interference in them. It was only once I switched them off that the interference stopped. I figured the a/c's noise-cancellation system (if the older DH8s even have them?) was causing the interference. Was this assumption correct or do the older Dash 8s not even have noice-cancelling technology?
Strathpeffer From United Kingdom, joined Jan 2007, 79 posts, RR: 0 Reply 7, posted (6 years 10 months 4 weeks 1 day 13 hours ago) and read 2194 times:
Reviewing prompotional literature from the manufacturer suggests that non-Q Dash 8s don't have an active noise and vibration supression system - I'm willing to be corrected on this because the brochures are not very specific.
I think they are fitted with a passive system though - dampers and the like that are turned to a fixed frequency; unlike on the Q aircraft, where the dampers are constantly 'retuned' to match the current conditions.