Sounds in nature are generally not perfectly represented by a simple sine wave. The assumption of a sine wave is often used for easy calculations and mathematical modeling because sine waves have well-defined properties and are mathematically tractable. However, in reality, sounds in nature are more complex and can be represented by a combination of multiple sine waves, each with different frequencies, amplitudes, and phases. This concept is known as the Fourier series or Fourier analysis.
When a sound is produced, it is often the result of various sources, such as different instruments or objects, and each source can contribute its own set of sine waves or harmonic components. The combination of these harmonic components creates a more complex waveform, often referred to as a complex waveform or a sound spectrum.
The complexity of natural sounds arises from factors such as the timbre, which is the quality that distinguishes different musical instruments or voices, and the presence of overtones and harmonics that give sounds their unique characteristics. The precise shape of the waveform and the spectrum of a sound depend on the specific properties of the sound source and the medium through which it propagates.
In summary, while the assumption of a sine wave is useful for certain calculations and simplifications, sounds in nature are generally more complex and can be represented by a combination of sine waves or other waveforms. The analysis of sound using Fourier analysis allows for a more accurate representation of natural sounds.