Lets talk about the sound barrier

Discussion in 'General Discussion' started by cycloneman, Jun 23, 2012.

  1. cycloneman

    cycloneman Well-Known Member

    Joined:
    Dec 16, 2008
    Messages:
    8,381
    Location:
    Louisiana
    YOu can see by the pic the condensation cloud caused by breaking the sound barrier.

    Question. Once you break the sound barrier, does it continue to make the crack noise as the aircraft is moving supersonic. Here it is another way.
    An aircraft, or object is approaching the sound barrier, once it hits the barrier there is a sonic boom. Does this boom still exist 30 miles down the road if the object is still supersonic? What i am getting at is this. Once you achieve the sonic boom and continue to move supersonic are you still boomin or is it over? I kinda have the idea that this is like a door your crossing into. I have a reason for asking this but I want to see if my thought holds water first.

    Attached Files:

    Last edited: Jun 23, 2012
  2. jack404

    jack404 Former Guest

    Joined:
    Jan 11, 2010
    Messages:
    17,575
    Location:
    Australia
    no as it is now faster than sound .. if you keep going up and down through the sound barrier yes..

    the footage i took that ended up on mythbusters shows that

    they did a follow up to the supersonic blast show and showed the footage i took here of f-111's overflying at super sonic speeds and busting windows but no sonic boom other than the air getting outta the way at sea level

    higher up and you'd never know they went by

    http://www.youtube.com/watch?v=rCzChbmJ4w4

    warning language of soldiers used ..
    Last edited: Jun 23, 2012
  3. geds

    geds New Member

    Joined:
    Mar 27, 2011
    Messages:
    3,706
    Glad you answered that Jack - I've always wondered about it too....

    And who knew you were Hollywood film maker! :D
  4. hjsmith00843

    hjsmith00843 Member

    Joined:
    Jun 23, 2012
    Messages:
    123
    Location:
    Myrtle Beach SC.
    I think the boom occurs with the sound actually reaches the location. I remember hearing sonic booms in Iraq many times. i would be at one camp and a friend of mine would be at another camp miles away and he would hear it after me by a min or 2.
  5. jack404

    jack404 Former Guest

    Joined:
    Jan 11, 2010
    Messages:
    17,575
    Location:
    Australia
    could be the same boom but heard in another area

    sound travels
  6. geds

    geds New Member

    Joined:
    Mar 27, 2011
    Messages:
    3,706
    fixed for ya Jack ;)
  7. cycloneman

    cycloneman Well-Known Member

    Joined:
    Dec 16, 2008
    Messages:
    8,381
    Location:
    Louisiana
    OK

    lets talk typ rifles now.

    cal does not matter for this discussion.

    typ 20" bbl and a bullet leaves the muzzel at 3000 fps

    somewhere inside that barrel probably in the first 6" the bullet is supersonic. Why is it that a rifle cant be suppressed if the bullet has broken the sound barrier within the first half of the bbl?

    Or am i wrong, can rifles be supressed?
  8. jack404

    jack404 Former Guest

    Joined:
    Jan 11, 2010
    Messages:
    17,575
    Location:
    Australia
    the round on a super sonic rifle will break the sound barrier

    but you can suppress ( not silence) the exhaust gasses which are a large part of the report

    and why folks who load for silencer hunting use a custom load for sub sonic

    my old mac 10 had the sionic kit on it but if you did not use sub sonic ammo it would make noise TAK TAK TAK and be audible but way less than non suppressed

    try it yourself if you can . .22 can's are easy to get or make , ( do it legit and pay the fee ) use both sub sonic ammo and regular , you'll notice it soon enough ..
  9. cycloneman

    cycloneman Well-Known Member

    Joined:
    Dec 16, 2008
    Messages:
    8,381
    Location:
    Louisiana
    Well i am just courious, here is why?

    First off i dont need to supress anything. I actually just ordered a pellet rifle for what i want to do.

    But I have been courious as to why i see military rifles with supressors on them if they cant stop the crack noise? I do understand that supressors will take away the pop of the primer and some of the other noise. But why would anyone be interested in shooting supersonic ammo and putting a supressor on the rifle? Distance maybe? When shooting far distance in New Mexico in the wind sound does not travel well. I guess this would camo you. So maybe i just answered my own question
  10. cycloneman

    cycloneman Well-Known Member

    Joined:
    Dec 16, 2008
    Messages:
    8,381
    Location:
    Louisiana
    OK

    Follow me here.

    I know that if you shoot a rifle in the wind the wind will take some of that sound away.

    Facts. There are 3 sound that are being produced when firing a rifle. The sound of the primer, the sound of the bullet crossing the sound barrier and the sound of the bullet again crossing the sound barrier when it slows down back to sub sonic speed.

    It seems to me that there is nothing you can do with the bullet slowing back down to sub sonic.

    But i think there is a way to stop the first crossing of the sound barrier. I dont think the modern way of using baffels will accomplish this. It seems to me that you would have to use some type of matieral to slow down the vibrations caused by the crossing of the sound barrier. I guess no one has thought outside the box yet to figure it out.
  11. jack404

    jack404 Former Guest

    Joined:
    Jan 11, 2010
    Messages:
    17,575
    Location:
    Australia
    take a look at the altsonic work done by metal storm , contrasting and diaopposed sound offset by a few milliseconds and you dont hear the round being fired , but when it costs as much as a nuke reactor to make a quiet gun that way its beyond balance to produce , even if it works well
  12. Charles Christensen

    Charles Christensen New Member

    Joined:
    Nov 13, 2011
    Messages:
    208
    Any object that is traveling faster than sound creates highly compressed shock waves that radiate around it in a cone shape with the apex at the object and the cone trailing behind. This shock wave exists as long as the object continues at supersonic speeds. As the shock wave gets dragged across the ground the sudden change in air pressure results in a sonic boom. As the intensity of the boom relies on speed (higher speed equals greater intensity), altitude (lower altitude means thicker air and greater intensity) and object mass (aircraft equals greater intensity and a bullet much less) a bullet will have a "crack" sound and an aircraft a "boom".

    Supersonic air travel failed because of the problem of dragging shock waves across populated areas. That is why the Concorde only did over-water flights.

    The cloud you see in the photo is the result of lower air pressure in the forming shock wave as moisture in the air condenses. This effect is easy to see along the tops of wings in videos of navel aircraft operations and does not require supersonic flight.
  13. Bobitis

    Bobitis Guest

    Excellent response Charles.

    A few years ago, Obie was stumping in Seattle for money (as he does every time he comes here). A couple from Eastern WA were flying back to Seattle in their float plane and landed in Lake Washington. Apparently this violated AF1's air space, even though it had been on the ground for hours, and fighters were scrambled. :eek:

    Mchord AFB is 40 miles south of me. Whidby Island Naval Airbase is 40 miles north. Where did the fighters come from? Portland Oregon. :rolleyes: So in order to get here in a timely manner, they went supersonic. The problem is, the couple had half their gear in their car before the support arrived.

    The ensuing 'boom' had people freaked out and actually shut down all 911 service in Pierce County (Tacoma). :mad: I work about 5 miles from Boeing Field (where AF1 stays) and I heard two booms as well (there were 2 fighters). It's obviously a rolling boom as Tacoma is 20 miles south.

    My question is, when does the booming stop?

    If these fighters were still supersonic while on top of AF1, they overshot their target by 50 miles. :p

    If yer a pilot and ya break the barrier, then slam on the brakes, does the wave wash back over you?
  14. gunslinger69

    gunslinger69 New Member

    Joined:
    Jan 7, 2012
    Messages:
    84
    Location:
    maine
    I would have assumed that if an object sustained exactly the speed of sound it would be as if it was pushing a continuous boom along its path of travel.
  15. Millwright

    Millwright Well-Known Member

    Joined:
    Jun 30, 2005
    Messages:
    1,917
    Depends upon the POV of the observer. A "sonic boom" is a propagating wave front. A series of observers along the flight path would hear the "boom" in sequence just as a series of observers would hear the same from a supersonic bullet passing. >MW
Similar Threads
Forum Title Date
General Discussion 2 cycle engine oil for outboards - lets talk Nov 20, 2012
General Discussion Lets have some fun. Oct 18, 2014
General Discussion Slow Motion Bullets Underwater Mar 10, 2014
General Discussion Hay all you guys in the ice and snow lets see Jan 4, 2014
General Discussion Lets see your DIY steel (and targets)? Jun 11, 2013

Share This Page