Have you ever shouted “Echo!” from the top of a mountain, an outlook point, or in a canyon? If you have, then you know that after a few seconds you will hear the sound you made bouncing back at you. Interestingly, there are several key factors that go into being able to hear this echo. There are many elements that influence sound, but the most common environmental factors that affect sound are the surrounding terrain and objects, wind, and temperature. At Whistles for Life, we know the importance of understanding what impacts sound because it could affect your ability to be heard in case of an emergency.
Sound is an energy that is transmitted through vibrations, and travels through longitudinal pressure waves in a material medium, such as air. The strength of sound, is measured by its intensity, denoted in decibels (dBs). For every 10dB increase, the loudness of the sound is doubled. For example, Whistles for Life’s safety whistle can reach 120dB, which by comparison means the whistle’s sound is twice as loud as the sound of a chainsaw from 3 feet away (running at 110dB). However, sound isn’t limitless like light is. Sound can only travel so far, and can be influenced by many factors, which can either help or hinder noise transmission. Whether you’re lost in the woods, walking in an unsafe part of town, or trapped in a building, knowing which factors influence sound can help you strategize your next course of action in those dire situations.
The largest impediment of sound is typically your surrounding environment. Objects will either absorb sound or reflect it in a different direction. When you find yourself in an emergency and need to signal for help, you will want to move away from objects that suppress and dampen sound, which are usually intervening objects with a large amount of surface area and acoustic absorption properties. Sound-absorbing objects typically have uneven surfaces that catch sound waves and bounce them within itself until the waves dissipate. For example, tall, thick trees and bushes will absorb sound well because branches and leaves are porous and they create a larger total surface area for the object. This is especially important to note in case you find yourself lost in a heavily wooded area, because the distance your sound will carry will be drastically shortened. On the other hand, flat, rigid surfaces such as concrete walls or sheet metal will tend to reflect sound rather than suppress it, because there are no uneven surfaces that can dissipate the sound. When you shout “Echo!” at the bottom of a canyon, your shout is echoed back because your sound waves travel unimpeded and bounce off the rock surfaces, returning the sound to you.
Imagine there was an earthquake and your building collapsed, trapping you and several people inside. You might be perfectly unharmed underneath a large oak desk, but it could take a long time for help to find you, let alone hear you, due to all of the objects and noises that separate you and the first responders. In addition to the debris trapping you inside, there could be a range of competing environmental noises such as emergency vehicle sirens and noise from generators and excavators, which can make it nearly impossible for people outside to hear you. Therefore, having an airhorn or whistle nearby can increase your chances of being heard and rescued. An easy way to implement this practice, in places such as your office, is to keep an airhorn by the fire extinguisher or tape a whistle to the bottom of your desk.
Sound can also be influenced by the wind. As mentioned earlier, air is a medium that sound can travel through. Wind, by definition, is the bulk movement of air, and it can move in different directions and speeds. Wind can carry noises farther away, prevent them from traveling as far, or even push them sideways, causing sounds to appear to come from a different location. For example, if you are at a distance from a friend on a windy beach, you might be able to hear everything he or she is saying clearly, but your friend isn’t able to hear you. Why is that? Wind travels at different velocities depending on the altitude. Wind that is lower to the ground moves at slower speeds, and this speed increases the higher it gets, which causes a “wind gradient.” This wind gradient means that sound traveling against the wind, or upwind, will be directed upwards and away from your intended target, transmitting the sound at a less effective level. While sound traveling in the same direction as the wind, or downwind, will be directed downwards and will maintain a higher level of sound. So, if you’re faced with a headwind, you might want to save your energy until the wind dies down or try shouting in a different direction. Contrarily, if you’re downwind, realize that the noise you make will be heard from a longer distance.
The last factor that affects sounds is temperature. The warmer the air temperature, the quicker sound waves will travel. The air molecules in warm air have more energy, meaning the molecules are vibrating quicker, which allows sound to travel through this medium much faster. In addition, sound that is traveling at a faster rate is less likely to be impeded or absorbed by obstacles. On the other hand, this means that sound won’t carry as far in colder temperatures. If you get lost snowshoeing, for example, be aware that your voice might not be heard as easily as it would if you were hiking in a canyon. As a result, you may want to consider bringing along additional safety tools that will help amplify your ability to call for help if necessary when partaking in activities in cooler temperatures.
If you need to grab someone’s attention and are only equipped with the sound of your own voice, you realistically would be able to reach a maximum volume of 110dB for about ten minutes. But at that level, you will quickly lose your voice. However, if you were equipped with some type of signaling device, such as a safety whistle, you could easily increase your sound level and reduce the amount of energy you exert.
At 120dB, Whistle’s for Life’s safety whistle will make your calls for attention twice as loud, for a much longer period. It is small and compact enough to carry with you at any time, and is extremely easy to use. If you can breathe, you can blow this whistle. In addition to the main chamber’s loud 120dB sound, our three-chambered whistle produces omnidirectional sounds at different frequencies through the two side chambers, giving you an even better chance of breaking through the ambient noises of your environment.
Therefore, consider bringing a signaling device with you on your next outdoor adventure, clipping one on your key-chain, or placing one in your desk at work. You never know when a situation will arise, but being prepared can increase your chances of being rescued when it does.