Years ago there was a thread here that talked about how lower pitched whistles can be heard farther than higher pitched whistles. I'll save you from having to search for the thread. It was determined that lower pitches can be heard farther. The example given was the car with the customized sound system. You know the one. The one that thumps bass all around the neighborhood and nearly shatters everyones windows. You can hear this car's bass for a long time before you ever hear any of its mid range speakers or its tweeters.

So since I knew that lower pitches can be heard further I kept an eye out for something that can produce a low pitch for use in an emergency kit. And I think I may have found two.

The Air Blast Horn.
It's an air horn that doesn't use a compressed air can. You blow into it.

Here's a do-it-yourself version.

Not sure if this will replace the whistle in an emergency kit, but it's good to have options.

As one with a major high freq hearing loss (no one used ear protection when shooting in the old days), I could not agree more...

Try out a Bo'sun's Pipe. It was designed to be heard by everyone regardless of where they were on a ship when it blew it's command songs.

All of these are made of brass, chrome plated, so it requires warming up before using in extreme cold, if you want to keep the skin on your lips.

The in-car installed bazuka style speakers are so loud in low range because the car itself works as a sound resonator (sound amplifier) for them. That's why the low pitch musical instruments are large or huge in size.

The ship horns are using the low pitch sound because it delivers more energy to work over longer range in heavyweight fog air. They have enough energy to move the vapor which always stays above the water surface.

But in the woods the long (low pitch) sound waves will be muffled by the dense trees and vegetation immediately even if you have the line of sight with the listener. The high pitch sound, in opposite, will go through much farther. It's also reflects from the natural surfaces much better.

Just elementary physics.

Interesting. I hadn't thought of that. I live in the desert south west where there is very little vegetation to absorb sounds. A low frequency sound signaler like an air horn may come be more suited to me than someone in the forest. But if I had to choose a mouth powered air horn or a whistle I'd probably go with the whistle only because it can be used in more places and it is smaller.

I like that idea, low pitch for old folks with lousy ears, high pitch to go farther in the woods...

Also keep in mind that most people with hearing damage have lost more off the low end than the high. Too much base, too few mufflers. A low sound CAN carry farther, but a higher pitched sound is more likely to be noticed if you don't have a regular pattern going.

For what it's worth...

High and Low are relative terms here. It's widely known that no adult hears evenly from 20 - 20k (the range in kiloHertz of frequencies most often talked about). In fact ALL of us have a hearing "curve".

Two guys (Fletcher and Munson from Bell Labs) back in the 30's discovered this human hearing curve and plotted it. We are much more sensitive to sounds in the 1k to 5k range. And that sensitivity varies with the volume of the sound. In other words... at very soft levels we hear almost exclusively in this range and both the highs and lows go away. That's why better stereo gear used to come with a variable loudness control; to actively compensate for this effect.

And the odd part? On average women have better hearing (less loss)than men. So we men tend to turn things up until it sounds "normal" to us (our curve flattens a bit). But by that point our wives hearing curves flattend out well before that point and they find it very loud.

So next time your wife yells at you for turning up the volume on the TV/Radio, just compliment her on her flatter Fletcher-Munson curve.

Hey, it might work...

I think it would be nice to have that curve here:


The frequency is on the X line (logarithmic scale).

The graph shows equal loudness curves (red) for a different sound intensity levels.

As you can see the approx. 3500 Hz frequency is the most efficient for a whistle.

Just a thought: if you're stranded in a ravine with a broken leg, luck will often determine who runs across you (assuming someone does, in time), and you won't know if they have hearing impairments. But I'm hoping that SAR would have decent hearing.

If YOU don't have good hearing, it doesn't matter too much if you're the one they're searching for. What YOU would need is something that THEY could hear.

So, I guess you might need both a woofer and a tweeter...

Sue

Alex,

Thanks for posting the loudness curves; visuals always help.

And 3.5kHz is indeed the area we are best at hearing. At the risk of offending anyone's beliefs...
... one common explantion for this is that mankind, being social by nature and for survival, has gotten exceptionally good at recognizing each other's voices.

In any event, it is in fact this frequency area that is most critical in determing "clarity" of the human voice. We simply hear best in the area that is most important to us. Design or chance, that's pretty cool.

So if I were to look for the "perfect" whistle... that is indeed the frequency range I would look for. To Susan's point, all of us are better at hearing in this range. All that changes is how much better (or worse) depending on volume, age, gender, etc.

Hope this helps,

Keep in mind, however, that in a choice between decibel level and frequency, decibel level is usually the deciding factor. In most practical cases, the difference between one whistle's frequency and another will be minimal. (The Storm and Windstorm whistles produce a 3.15 KHz tone, if I remember correctly.) However, decibels are logarithmic, and 105 dB (Storm Whistle) is a little over 3 times louder than 100 dB (competition).

You are right on the money... assuming we are talking about signal whistles here. We got pretty far afield, but the thread started as a discussion of air horns vs signal whistles.

The fact is that both frequency and SPL matter. If the frequncy of the signaling device falls outside of the "sweet spot" of human hearing, the SPL level needs to be MUCH higher in order to be heard as well. Most airhorns run in the 500Hz to 250Hz range. At those frequencies, human hearing can be off 30dB or more when sounds are very faint. That's why you see SPL levels for things like boat horns at 125dB or more.

And while low frequencies do have a tendency to travel further, the energy requied to produce those super high SPLs at low frequencies is simply not practical/possible for portable devices.

So the bottom line for all these numbers is what exactly?

Just as JC suggests... get a whistle whose pitch falls into the human sweet spot of hearing (most do) and go for the loudest one of those you can carry comfortably.

Hope this helps,

A fantastic piercingly loud emergency whistle is simply an empty (fired) SKS rifle cartridge. You basically put it up against your lower lip and sort of blow into and across the top kind of like making sound by blowing into the top of a pop bottle.

One thing to also remember about cars with loud bass, those subwoofers are pushing lots of power. My four car speakers each get 40 watts, while, each of my two subs runs on 200 Watts. There's a lot of power shoved into the low freqs.