what makes a cannon loud?

[bluez]

Is this only determent by the amount of powder used?
When comparing guns it seems that the ones with the shortest barrel is loudest.
However i have an impression that lets say a 1" cannon loaded with 300 grains of ff
and a 2" cannon with the same amounts of ff sounds different?

[Double D]

The velocity of the powder gases as they exit the barrel determines how loud the boom is.  It also take a little bit of resistance to ramp up up the pressure.

Loose powder will just go whoosh out a barrel. Put a single thickness of tight fitting cardboard over the powder and you will get a boom.  Put the whole thing in a thunder mug and you will get bigger boom.

[Artilleryman]

Sound is affected by bore size, barrel length, type of powder, amount of powder, elevation on the barrel (how close the muzzle is to the ground which absorbs sound), and the use of a projectile or wad.

It would be interesting to have decibel meter measure the sound.  It would also be interesting to measure the pitch of the sound.

[gary michie]

Hi
We have 2 full size cannons on the field at reenactments a 10lb parrott and a 12 lb mountain howitzer we use a 6 oz, charge in both. we roll the rounds in to a VERY HARD ball and try to be consistant. on the whole the M.H. is by far LOADER, no one likes to stay at there posts and the parrott which was the loudest 6 oz shooter in the WCWA is now a ok second.
gary

[Cat Whisperer]

I have access to dB meters & will measure a few next time I'm out shooting.

Suggest using the "A" scale (vs. the C scale) as it parallels the curve of the human ear.  Also suggest, for making comparisions, on recording the direction of the microphone, the distance from and orientation to the cannon.  That would make comparisons fair.

It's my impression that the larger the bore the deeper the boom.  It would be interesting to do a spectral analysis of various mortars/cannons.

AND, BlueZ -  WELCOME to the board!

[Artilleryman]

When we were doing the sounds for Master and Commander we blew out a couple of the mikes placed near the 12 pdr Napoleon. 

[Cat Whisperer]

When we were doing the sounds for Master and Commander we blew out a couple of the mikes placed near the 12 pdr Napoleon. 

Good to know!  How far away and what orientation?

[Artilleryman]

I think the ones they blew out were slightly in front of and to the sides of the piece.  I think they moved them back behind the muzzle, but I will have to look to see if I have photos that would show placement.


Just looked for photos, and realize that the photos taken were pre-digital camera.   Have to go through albums and scan photos in if there are any that answer the question.

[Cannoneer]

Hi
We have 2 full size cannons on the field at reenactments a 10lb parrott and a 12 lb mountain howitzer we use a 6 oz, charge in both. we roll the rounds in to a VERY HARD ball and try to be consistant. on the whole the M.H. is by far LOADER, no one likes to stay at there posts and the parrott which was the loudest 6 oz shooter in the WCWA is now a ok second.
gary

Gary,
Was the judgement on the loudness of both cannon reached when they were firing projectiles, and is the Parrott rifled?

[bluez]

I could be wrong, but i have a feeling that mortars is always deeper in pitch than cannons, even the smaller ones.

[Zulu]

I used to shoot 12 oz. out of my smooth bore Parrott for a very nice, loud, report.
I shot next to a Wiard rifle (smoothbore) shooting 8 oz. which matched mine.   It depends on the gun.  Both were 3" bores.
Zulu

[Cat Whisperer]

I could be wrong, but i have a feeling that mortars is always deeper in pitch than cannons, even the smaller ones.

bluez -  WELCOME to the board!  I love the deep boooom of my 4.5" coehorn - but it's nothing compared to standing next to a 155mm self-propelled howitzer!

In general, the shorter the barrel the more intense the blast - exceptions as above, of course.   

[gulfcoastblackpowder]

You may want to look at these threads, which both discuss a cannon's report at length (though most of it is speculative, since none of the input was by accoustic engineers):

http://www.gboreloaded.com/forums/index.php/topic,211996.0.html
http://www.gboreloaded.com/forums/index.php/topic,209547.0.html

[Artilleryman]

When we were doing the sounds for Master and Commander we blew out a couple of the mikes placed near the 12 pdr Napoleon. 

Good to know!  How far away and what orientation?

This is the placement of the mic on the 24 pdr howitzer after the mic got blown earlier on the 12 pdr Napoleon.

[gulfcoastblackpowder]

Wondering why the cloth is taped on the gun...    (I could guess, but I'd probably be wrong.)

[Artilleryman]

Bronze smoothbores make a ringing noise as the projectile leaves the bore.  In the movie all the guns are iron guns that do not make that sound.  So to be as authentic as possible (sound wise) we wrapped a piece of carpet around the chase of the barrel.  We also had to tape down all the moving metal parts that made clanking, rattling noises that you would not hear from a gun truck.   

[Cat Whisperer]

Ooooofda!

THAT's CLOSE! 

[Artilleryman]

They also had a larger mic located to the side and rear of the piece.

[gulfcoastblackpowder]

Bronze smoothbores make a ringing noise as the projectile leaves the bore.  In the movie all the guns are iron guns that do not make that sound.  So to be as authentic as possible (sound wise) we wrapped a piece of carpet around the chase of the barrel.  We also had to tape down all the moving metal parts that made clanking, rattling noises that you would not hear from a gun truck.   

Makes sense.  Those foleys are interesting people!

[Parrott-Cannon]

Sound traveling through air is merely a sequence of high and low pressure zones stacked back to back. When something vibrates to produce sound (like the surface of a bell that has just been rung), the air surrounding the object also gets pushed back and forth. When the bell's surface vibrates outward, it squeezes the air just outside the bell. When it vibrates inward, it rarifies (or "un-squeezes") that same air. As it vibrates back and forth the compressions and rarefactions move outward from the surface of the bell, at the speed of sound. Our eardrums are affected by these compressions and rarefactions, and our nerves transmit the information to our brains, which decode it as sound.

For a little bell, the difference between the compressed air and the rarified air isn't that great, so the sound waves don't carry much potential to vibrate your eardrums. For an cannon, it's a different story.

The energy of the hot gases exiting a cannon push suddenly and violently on the air at the muzzle, and  this causes a very high-pressure wave to spread outward. There's a very low-pressure zone right behind that wave, so when these waves hit your eardrum there's a tremendous difference between the compressed air and the rarified air.  We hear it as a BANG!

The math:

There are four properties that are characteristic of a sound waves:  The velocity, frequency, wavelength, and amplitude.  The following equation addresses three of the variables.

velocity = frequency X wavelength   the velocity is the velocity of sound about 1118 feet per second at STP.  The frequency and wavelength are energy related.  Increases in either the frequency or wavelength indicate an increase in energy,

The amplitude and wavelength are caused by the pressure, temperature, and mass of the gas exiting the muzzle.  Bigger rocks thrown into a pond at a higher velocity cause bigger waves with a longer frequency.

The frequency or tone is controlled by the duration of the pressure pulse (Time).

The velocity of the gasses exiting a barrel can be expressed as

gas velocity = Pressure X Area X Time/Mass of the Gas

This equation to be solved accurately requires a computer and the use of numerial analysis.  However, if we examine the equation we see the following:

The energy contained in the gas:

Energy = 0.5  X  (Pressure X Area X Time)^2 / Mass of the Gas

The energy of the gas is increased by Pressure, Area (bore), Time, Mass of the Gas.

Time in this case is the pulse time of the pressure wave.

There is also a secondary explosive sound as the unburnt powder ignites, and if the ball bounces along the barrel there is a ring effect like a bell.

[Cat Whisperer]

I've noticed that the ring occurs when the wall thickness is thin.  (at least two of my mortars ring - both steel)

[Parrott-Cannon]

I've noticed that the ring occurs when the wall thickness is thin.  (at least two of my mortars ring - both steel)


The ringing effect is dependent on the material tickness and the modulus of elasticity for the barrel.

[Cannoneer]

In Europe and England from the 13th to the 17th centuries many alchemists and cannoneers might have honestly answered that question with the word magic.

[Cat Whisperer]

I've noticed that the ring occurs when the wall thickness is thin.  (at least two of my mortars ring - both steel)

The ringing effect is dependent on the material tickness and the modulas of elasticity for the barrel.

Which is to say they likely all ring, but most are rigid enough (from thickness OR material) so that it isn't loud enough to perceive considering the other atmospheric disturbances.  Thanks for adding the term modulas of elasticity - that adds to our knowledge base.

[gulfcoastblackpowder]

I've noticed that the ring occurs when the wall thickness is thin.  (at least two of my mortars ring - both steel)

The ringing effect is dependent on the material tickness and the modulas of elasticity for the barrel.

Which is to say they likely all ring, but most are rigid enough (from thickness OR material) so that it isn't loud enough to perceive considering the other atmospheric disturbances.  Thanks for adding the term modulas of elasticity - that adds to our knowledge base.

To complete the addition to the knowledge base, for those who may not be familiar with the term, modulus of elasticity, spelled with 2 u's and no a's, indicates the ability of a material to strain (or stretch non-permanently) under stress.

While you are right, that all cannons will ring to some degree, some materials lend themselves more to it than others.  The lower the modulus, the easier it is for the material to flex under loading.  This flexing and is what causes the vibrations Parrott referred to, and is what causes the gun to ring.  For instance, Brass has a Young's Modulus of 100-125 while Iron and Steel are 190-210.  That is why, for a given geometry, a brass cannon will sing more than a steel or iron one. 

Of course, the vibration of the gun isn't the cause of all the noise from firing a cannon - most of the noise is from the powder and the conditions of it's use (grain size, volume of powder, wadding, bore size, bore length, etc.).

[bluez]

The energy of the hot gases exiting a cannon push suddenly and violently on the air at the muzzle, and  this causes a very high-pressure wave to spread outward. There's a very low-pressure zone right behind that wave, so when these waves hit your eardrum there's a tremendous difference between the compressed air and the rarified air.  We hear it as a BANG!

The math:

There are four properties that are characteristic of a sound waves:  The velocity, frequency, wavelength, and amplitude.  The following equation addresses three of the variables.

velocity = frequency X wavelength   the velocity is the velocity of sound about 1118 feet per second at STP.  The frequency and wavelength are energy related.  Increases in either the frequency or wavelength indicate an increase in energy,

The amplitude and wavelength are caused by the pressure, temperature, and mass of the gas exiting the muzzle.  Bigger rocks thrown into a pond at a higher velocity cause bigger waves with a longer frequency.

I have two cannons in 1"  bore, one with a barrel length around 14" the other as short as 4". And the 4" barrel makes a much louder sound than the 14" with the same amount of powder, but i am still wondering where the physics plays in her, is it because some of the powder is still burning outside the shorter barrel?

[GGaskill]

... is it because some of the powder is still burning outside the shorter barrel?

Most likely it is because more of the expansion of the gasses takes place in the air than in the bore.

[Parrott-Cannon]

The energy of the hot gases exiting a cannon push suddenly and violently on the air at the muzzle, and  this causes a very high-pressure wave to spread outward. There's a very low-pressure zone right behind that wave, so when these waves hit your eardrum there's a tremendous difference between the compressed air and the rarified air.  We hear it as a BANG!

The math:

There are four properties that are characteristic of a sound waves:  The velocity, frequency, wavelength, and amplitude.  The following equation addresses three of the variables.




velocity = frequency X wavelength   the velocity is the velocity of sound about 1118 feet per second at STP.  The frequency and wavelength are energy related.  Increases in either the frequency or wavelength indicate an increase in energy,

The amplitude and wavelength are caused by the pressure, temperature, and mass of the gas exiting the muzzle.  Bigger rocks thrown into a pond at a higher velocity cause bigger waves with a longer frequency.

I have two cannons in 1"  bore, one with a barrel length around 14" the other as short as 4". And the 4" barrel makes a much louder sound than the 14" with the same amount of powder, but i am still wondering where the physics plays in her, is it because some of the powder is still burning outside the shorter barrel?

There are two factors at play.

The maximum pressure avehived very quickly and the amount of powder burnt is dependent on barrel length.  So with the shorter barrel you have a higher pressure pulse and more unburnt powder that will explode after the projectile leaves the barrel.

[Parrott-Cannon]

I've noticed that the ring occurs when the wall thickness is thin.  (at least two of my mortars ring - both steel)

The ringing effect is dependent on the material tickness and the modulas of elasticity for the barrel.

Which is to say they likely all ring, but most are rigid enough (from thickness OR material) so that it isn't loud enough to perceive considering the other atmospheric disturbances.  Thanks for adding the term modulas of elasticity - that adds to our knowledge base.

To complete the addition to the knowledge base, for those who may not be familiar with the term, modulus of elasticity, spelled with 2 u's and no a's, indicates the ability of a material to strain (or stretch non-permanently) under stress.

While you are right, that all cannons will ring to some degree, some materials lend themselves more to it than others.  The lower the modulus, the easier it is for the material to flex under loading.  This flexing and is what causes the vibrations Parrott referred to, and is what causes the gun to ring.  For instance, Brass has a Young's Modulus of 100-125 while Iron and Steel are 190-210.  That is why, for a given geometry, a brass cannon will sing more than a steel or iron one. 

Of course, the vibration of the gun isn't the cause of all the noise from firing a cannon - most of the noise is from the powder and the conditions of it's use (grain size, volume of powder, wadding, bore size, bore length, etc.).

Thank you correcting my spelling.  I am the worlds worst speller.  What I do not understand is why the ball bounces in the barrel.  Conservation of momentium sugests that a smooth ball fired from a smooth barrel would simply role down the barrel.  I do known, the roughness of the barrel and ball play a major role in the velocity a cannon acheives.  I have a golf ball parrott and a golf ball french 75.  The parrott produces a velocity of 672 fps while the french 75 acheives a velocity of 811 fps using golf balls for ammo and a 400 grain charge of cannon grade powder.  The barrel on the parrott is rough while the french 75 has a very smooth barrel (the friction factor).  Do you find more ringing with smooth barrels?

My parrott has a heat fitted band and produces high pressure reading that do not reflect the powder charge.  I beleive this is cause by amplication of the ringing caused by the bell within a bell effect of the band construction.

[gulfcoastblackpowder]

I think there are a few reasons the ball would bounce:

1: The ball is slightly rolling out the tube due to elevation - unless the gun is pointed at exactly 90* to the Earth, gravity will be acting on the ball while the powder does, keeping it wanting to roll out the bottom of the bore as it is being pushed by the powder.

2. Inconsistencies in the ball and bore surface - as you mentioned, there are no truly smooth balls or bores.  They can be very smooth, but there will always be some variations - if nothing else, fouling, which will tend to interfere with the ball's desire to maintain a rolling position on the bottom of the bore as described before.

3. Inconsistencies in the packing and powder - even just a small deviation in how the powder is packed could cause a difference in the loading of the force it generates on the ball.  If the loading isn't exactly colinear to the bore, it will tend to induce spin on the ball, which will magnify the effect described in #2.  In fact, even if the pressure does act colinearly to the bore, gravity acting on the ball will still tend to induce rolling, as the net forces will be slightly downward.

4. While rolling OR sliding, a 3rd force is acting on the ball - friction.  Because friction force will be higher where contact between ball and bore is predominant, it will tend to slow down the ball on the bottom, while the blast continues to push - in fact - overpowering the friction to the point that the ball bounces off the bottom of the bore.

This bouncing is eliminated in rifled bores because the rifling holds the projectile tighter, forcing it to have a controlled roll - in the form of the rotation it imparts.

As far as the resonance sound between rifled and smooth bores, I haven't done a direct comparison, but I'd have to guess that the smooth bore will be louder if for no other reason than the rifling will limit the amount of vibration the cannon can sustain.