# Sound wave -- positive and negative frequency?

• btb4198
In summary, the conversation discusses the Fourier transform and how it applies to sound waves. The speaker mentions that taking the Fourier transform of a sine wave results in a spectrum plot, and wonders if the same holds true for sound waves from speaking or singing. The other person confirms that this is likely the case and explains that it is a mathematical artifact of how the Fourier transform is calculated. They also provide an example of a power spectral density plot for a square wave.
btb4198
does ever sound wave have a positive and negative frequency?

btb4198 said:
does ever sound wave have a positive and negative frequency?
Sure. Are you familiar with the Fourier transform?

berkeman said:
Sure. Are you familiar with the Fourier transform?
yes, I am. why do you ask ?

btb4198 said:
yes, I am. why do you ask ?
Because when you take the Fourier transform of a sine wave, you get a spectrum plot like this:

I know it is right for a sinwave, or you saying it is the same for sound wave? like someone talking or singing?

## 1. What is a sound wave?

A sound wave is a type of mechanical wave that travels through a medium, such as air or water, and carries energy from one place to another. It is created by vibrations or disturbances in the medium, which cause particles to move back and forth, creating a wave-like pattern.

## 2. What is positive frequency in sound waves?

In sound waves, positive frequency refers to the number of complete cycles or vibrations per second. It is measured in Hertz (Hz) and is directly related to the pitch or perceived frequency of a sound. Higher frequencies result in higher pitched sounds, while lower frequencies result in lower pitched sounds.

## 3. What is negative frequency in sound waves?

Negative frequency in sound waves is a concept used in signal processing and mathematics. It is the opposite of positive frequency and is represented by a negative number. In sound waves, negative frequency can be observed when a sound wave is inverted or reflected, resulting in a phase shift.

## 4. How do positive and negative frequencies affect sound waves?

Positive and negative frequencies play a crucial role in shaping sound waves and determining their characteristics. For example, the combination of positive and negative frequencies can result in interference patterns, which can amplify or cancel out certain frequencies in a sound wave, affecting its overall loudness and quality.

## 5. Can we hear negative frequency in sound waves?

No, we cannot hear negative frequency in sound waves. Negative frequencies are a mathematical concept used to describe certain characteristics of sound waves, but they are not audible to humans. Only positive frequencies within the audible range of 20 Hz to 20,000 Hz can be heard by the human ear.

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