![]() ![]() ![]() ![]() The reference intensity I 0, corresponding to a level of 0 decibels, is approximately the intensity of a wave of 1,000 hertz frequency at the threshold of hearing-about 10 -12 watt per square metre. Here L represents decibels, which correspond to an arbitrary sound wave of intensity I, measured in watts per square metre. Such a scale is provided by the sound intensity level, or decibel level, of a sound wave, which is defined by the equation Because of the enormous nonlinearity of the ear in sensing pressure waves, a nonlinear scale is convenient in describing the intensity of sound waves. The ear mechanism is able to respond to both very small and very large pressure waves by virtue of being nonlinear that is, it responds much more efficiently to sounds of very small amplitude than to sounds of very large amplitude. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today. ![]() Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.The above equation shows that the two sound waves having the same sound intensity but different frequencies have the same pressure amplitude. The change in volume is $\Delta V = (y_2 - y_1)A' = \Delta yA'$ and the initial volume is $V = \Delta x A'$. In our case consider that the volume decreases or the gas is compressed ($y_2 < y_1$) and the pressure increases. The volume of the gas decreases when $y_2 y_1$ (rarefaction). Figure 1 The pressure variations of a sinusoidal wave is sinusoidal. As the sound wave given by the wave function $y = A \cos (kx - \omega t)$ passes through the cylinder, the left end undergoes a displacement of $y_1$ and the right end undergoes a displacement of $y_2$ at time $t$. The left end of the cylinder is at $x$ and the right end is at $x \Delta x$ in our coordinate system. To express the sinusoidal pressure variations of a sound wave, we consider a cylindrical element of gas of length $\Delta x$ and cross-sectional area $A'$ as shown in Figure 1. You'll see that the pressure variations of a sinusoidal sound wave is again sinusoidal. The sound is better described in terms of its pressure variations than displacement variations. The sound wave travels in the form of successive compressions and rarefactions. ![]()
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