Low Frequencies

Slow movement requires larger displacement to create the same pressure variance that can be produced by smaller displacements at higher velocity.

Most people can hear down to a lower limit between 18Hz and 24Hz (usually attributed as 20Hz nominal value) but be aware of the effect of the modified Fletcher-Munson curves.

The woofers in my Shure IEMs are quite a bit smaller than my eardrums, but they seem to manage pretty well.

They're operating in compression mode, not in open air mode.  Take them out of your ear canals and see how they sound!

Generating low frequency waves (low notes) takes power and simple physics (large diamater cones, moved by a lot of power).

Hearing them is a bit easer than generating them.

@Huge: thanks for pointing me back to the thread 

In addition to the mechanics in the generation of low fs pressure waves,  measuring the wave is entirely different,  its not size dependant.   The ear drum is sensitive to the tiny changes in air pressure carried in a sound wave.    Humans have an audio system & brain tuned to hear this as sound. We have an audio bandwidth limited to aprx 20Hz-20kHz,  however other animals larger than humans have higher low frequency hearing limits,  the exception is elephant at 16Hz,  outside that few hear as low as humans.      

Also think about a microphone ribbon,  a tiny alloy foil,  does the same job as an eardrum.

Dogs 40Hz - 40kHz
Cats 40Hz - 77kHz

Huge posted:

Dogs 40Hz - 40kHz
Cats 40Hz - 77kHz

Cow 25Hz   Horse 55Hz   ..........      

The other point is that the human ear is sensitive to pressure induced deflections that are as minute as 1/2 the diameter of a hydrogen molecule!  So it doesn't take much pressure to cause sufficient deflection for us to hear something.
(A cat can still beat this easily!)

Actually in sound energy terms we're about 100 times less sensitive at low frequencies than we are at mid frequencies, so the small size of the eardrum does have the effect of reducing efficiency at low frequency.

Mike-B posted:

Huge posted:

Dogs 40Hz - 40kHz
Cats 40Hz - 77kHz

Cow 25Hz   Horse 55Hz   ..........      

     Elephant 14Hz

TOBYJUG posted:

Mike-B posted:

Huge posted:

Dogs 40Hz - 40kHz
Cats 40Hz - 77kHz

Cow 25Hz   Horse 55Hz   ..........      

     Elephant 14Hz

I'll see your 14Hz elephant & raise you a 3Hz Sumatran Rhino

........... ??? I wonder how they got an elephant to press the little hearing test button without breaking it ???  

Not exactly to do with low frequencies, but an interesting article about the worlds loudest soundsystem.

https://thump.vice.com/en_uk/a...dsystem-in-the-world

I expect some knob head would put in a cheap looking Japanese drift replica car. 

Darwinian evolution theory suggests that each creature will have a hearing range that maximises the survival of the species. Treats from predators, finding food, finding a mate are factors. Whales may have even lower sensitivity than elephants as their songs travel long distances in the oceans. 

Incidentially, the energy in a sound wave is proportional to its amplitude and the square of the frequency, hence woofers need larger longitudinal displacements and/or area to produce the required sound energy. The mass and stiffness of the cone and coils will come into play also. Similar factors apply to the ear.

Phil

Filipe posted:

Darwinian evolution theory suggests that each creature will have a hearing range that maximises the survival of the species. Treats from predators, finding food, finding a mate are factors. Whales may have even lower sensitivity than elephants as their songs travel long distances in the oceans. 

 

I like the idea of that - though I have only heard of it in relation to humans as predators, using a bait to lure the victim. ()

There are some predators like the monkfish (but not as applied to HiFi systems) that use lures, although it (usually) manages to snatch the lure away at the last moment!

I interpret lures differently from treats: the latter suggest receiving and enjoying what is offered, whether being given sweets or being taken somewhere enjoyable ... 

Threats not treats! Cursed autocomplete or lack of attention! Sorry to spoil the imaginative thought processes!

Phil

Another set of data with slightly different values. 

I am glad I am not a mouse bat or beluga whale as vocal recognition could be impaired.

Species Approximate Range (Hz)
human 64-23,000
dog 67-45,000
cat 45-64,000
cow 23-35,000
horse 55-33,500
sheep 100-30,000
rabbit 360-42,000
rat 200-76,000
mouse 1,000-91,000
gerbil 100-60,000
guinea pig 54-50,000
hedgehog 250-45,000
raccoon 100-40,000
ferret 16-44,000
opossum 500-64,000
chinchilla 90-22,800
bat 2,000-110,000
beluga whale 1,000-123,000
elephant 16-12,000
porpoise 75-150,000
goldfish 20-3,000
catfish 50-4,000
tuna 50-1,100
bullfrog 100-3,000
tree frog 50-4,000
canary 250-8,000
parakeet 200-8,500
cockatiel 250-8,000
owl 200-12,000
chicken 125-2,000

 I read somewhere once that the low rumble given by an elephant can be heard by another elephant up to 10 miles away but its to low for us to hear unfortunately!

elkman70 posted:

Another set of data with slightly different values. 

I am glad I am not a mouse bat or beluga whale as vocal recognition could be impaired.

Species Approximate Range (Hz)
human 64-23,000
dog 67-45,000
cat 45-64,000
cow 23-35,000
horse 55-33,500
sheep 100-30,000
rabbit 360-42,000
rat 200-76,000
mouse 1,000-91,000
gerbil 100-60,000
guinea pig 54-50,000
hedgehog 250-45,000
raccoon 100-40,000
ferret 16-44,000
opossum 500-64,000
chinchilla 90-22,800
bat 2,000-110,000
beluga whale 1,000-123,000
elephant 16-12,000
porpoise 75-150,000
goldfish 20-3,000
catfish 50-4,000
tuna 50-1,100
bullfrog 100-3,000
tree frog 50-4,000
canary 250-8,000
parakeet 200-8,500
cockatiel 250-8,000
owl 200-12,000
chicken 125-2,000

I can't help to imagine how on earth they established these responses.. also many creatures including us don't hear using our ears very low frequencies but feel them instead...Humans experience frequencies well below 64 Hz... 

Simon-in-Suffolk posted:

I can't help to imagine how on earth they established these responses.. also many creatures including us don't hear using our ears very low frequencies but feel them instead...Humans experience frequencies well below 64 Hz... and I am not aware of anyone being able to hear up to 23kHz 

  I raised that same question earlier today  ........... ??? I wonder how they got an elephant to press the little hearing test button without breaking it ???  

Simon-in-Suffolk posted:

I can't help to imagine how on earth they established these responses.. also many creatures including us don't hear using our ears very low frequencies but feel them instead...Humans experience frequencies well below 64 Hz... 

When the ear receives a pulse of sound at a given frequency to which it can respond, then for a short time after it emits a lower energy signal.  It's called the Otoacoustic emissions test.

Ardbeg10y posted:

This question popped up in my mind recently:

Why do we need large woofers to generate low frequency tones, but can our tiny eardrum hear them?

Ardbeg10y

We don't need large woofers; a decent pair of in-ear h/phones will generate v good LF tones. An acceptable amount of wine precludes me expanding on that answer for now.

ChrisR_EPL posted:

Ardbeg10y posted:

This question popped up in my mind recently:

Why do we need large woofers to generate low frequency tones, but can our tiny eardrum hear them?

Ardbeg10y

We don't need large woofers; a decent pair of in-ear h/phones will generate v good LF tones. An acceptable amount of wine precludes me expanding on that answer for now.

As stated previously, they're operating in compression mode, not in open air mode.  Take them out of your ear canals and see how they sound!

Filipe posted:

Darwinian evolution theory suggests that each creature will have a hearing range that maximises the survival of the species. Treats from predators, finding food, finding a mate are factors. Whales may have even lower sensitivity than elephants as their songs travel long distances in the oceans. 

As you bring up the point of evolution, whales and elephants .... it's interesting to note that the two are thought to share evolutionary lines.