Density of air effect on fireworks

[lostfido]

Kinda goofy question, but do sounds change in intensity due to air temps????

 

I know in my years of racing that relative air density has a huge effect on horsepower but is there any effect on sound output as temps increase or decrease?

 

Also can/do fireworks benefit from additional oxygen? I know that they are a source of their own but would the addition of more oxygen create a change? For instance a fire burning in a firepit will burn just fine on its own, but if you add additional oxygen the fire burns bigger/hotter due to the additional oxygen.

 

I have asked this on another forum and gotten mixed results so I thought I would try here.

[Peret]

Atmospheric oxygen has a negligible effect on fireworks, which depend on their own carried oxygen. I can hardly believe a difference in the density of the air, in any place where people can breathe it unaided, has any effect at all. Fireworks perform pretty much the same in Denver and Albuquerque as they do at sea level.

[californiapyro]

certain types of stars do require on environmental oxygen for their effect (EG charcoal streamer-type comps) but unless you fired them in space there would be little to no difference IMO Edited January 29, 2012 by californiapyro

[Arthur]

At an altitude where people could live fireworks will work, some stars certainly do need atmospheric oxygen to completely burn. At extreme altitudes even BP ceases to function properly so it has little use for space propulsion!

[Mumbles]

I think he was asking about how sounds are affected, not if the performance is affected. I will say however related to temperature that I have had issues when shooting at low temperatures. I just don't think BP has the same oomph when it's cold. My club has a shoot in mid-March in northern Wisconsin. Lostfido may be able to give a better idea, but when we shoot at night I'd say the temperature is normally around 20F or so. My shells made with commercial 2FA were lifting awfully low a few years ago. These were 4" ball shells which may have been part of the problem. I'm using 4FA sized lift next time I bring stuff to this shoot.

 

Now, yes, to some level the temperature could have some effect on the intensity of the sound. The speed of sound is a function of temperature. At different temperatures the sound could seem more or less intense due to this. I notice this with salutes sometimes. They have different apparent pitches depending on if it's hot or cool.

[dan999ification]

i always thought that salutes sound sharper in cold weather better with snow on the ground.

tigertail stars etc need atmospheric air to function properly the oxygen content in the star will help ignite the charcoal before it leaves the star the air does the rest, adding more oxidizer would ruin its effect and kill the tail, the oxygen balance must be just that for things to work as intended.

adding more oxygen/more oxidizer/stronger oxidizer to a fire or a star will increase the burn speed to a point but too much oxygen/the wrong type of oxidizer and the effect is ruined for a number of reasons depending which, it could slow or go out

atmosphere is under 20% oxygen iirc most oxidizers have more than 20%, the difference of atmospheric air on a star would only be noticable if the atm had a higher ox content than the oxidizer [some cases] willing to be wrong on this

pyro comps are designed to function as is more oxygen is a benefit in some comps [that already have it] but not in others [that dont]

 

dan.

[NightHawkInLight]

There's no doubt that the sound of fireworks is effected by air temperature. Cold air is at a higher density and so sound will travel faster through it, which at the very least would make a noticeable difference in how echos sound. I believe a good portion of any sound you hear in a normal firework venue is a result of echos, many of them being from objects close enough to the audience that they are at an indistinguishable interval from the original sound, so those echos bouncing back even faster would build on the original sound waves. When you have snow, many of the echos bouncing at odd angles off the ground are softened and you end up with a much crisper and accurate tone to the original sound the fireworks are producing. That's my semi educated guess anyway.

[Potassiumchlorate]

You hear more on a cold day, but not with snow. I can tell from some experience of a cold, snowy country.

 

You will get the best sound and most echoes if firing over a silent water on a cold day without any snow, preferrably with some mountains or at least hills to echo against.

[SB15]

Cold air is at a higher density and so sound will travel faster through it

 

Actually, the SOS in a gas is proportional to the square root of its (absolute) temperature. The equation looks something like v = (kRT/M)^1/2, where v is the SOS, k is a constant specific to the gas, R is the universal gas constant, T is the absolute temperature, and M is the molar mass of the gas. In simple terms, this means that a higher temperature will result in a higher speed of sound.

 

As for the original topic, I'm certainly no expert on acoustics, but I suspect that air temperature will affect the tone of a report more than the intensity. Firing a salute or similar in cold air will result in a slower moving sound wave, which will likely be perceived as deeper and possibly louder by a human ear at close proximity, but it may fall off in intensity more quickly as it moves away from the origin of the blast. If this cold air is accompanied by snow on the ground, the report may sound quite sharp with minimal echoing, as snow (especially the low density powdered material) functions as an effective acoustic suppressor, absorbing sound energy rather than reflecting the wave.

[NightHawkInLight]

Actually, the SOS in a gas is proportional to the square root of its (absolute) temperature. The equation looks something like v = (kRT/M)^1/2, where v is the SOS, k is a constant specific to the gas, R is the universal gas constant, T is the absolute temperature, and M is the molar mass of the gas. In simple terms, this means that a higher temperature will result in a higher speed of sound.

 

Huh, I can't seem to find that particular equation, but a little searching revealed that I had things backward about the speed of sound related to density.

[lostfido]

Thanks for the replies guys!!!!

 

Any thoughts on the amount of oxygen playing a part????

 

"For instance a fire burning in a firepit will burn just fine on its own, but if you add additional oxygen the fire burns bigger/hotter due to the additional oxygen."

 

Could this effect the burn rate of certain burst/star comps? I know it probably isn't the most important question ever asked but my curiosity gets the best of me during the winter.

 

Anyone familiar with oxygen carriers used in fuels etc....????

[NightHawkInLight]

Well there's no doubt that if the atmosphere had a greater percentage of oxygen that the effects would be different...At a minimum, the tails on stars would burn away more quickly. I don't believe most star compositions would need adjustment though. As stars burn away the gasses that are expelled likely push away the atmosphere, meaning an increase or decrease in environmental oxygen would not be able to get close enough to the burning body of the star to make much of a difference. If I'm wrong and the atmosphere is able to make a difference, I don't think the density of cold air would cause an increase in burn rates even though there would be more oxygen in close proximity to the star. The cold in general would offset that available oxygen by slowing the reaction rate from what it would be at higher tempratures.