What is the difference between amplitude and intensity

High-pitch means small wavelength, and the size of a musical instrument is directly related to the wavelengths of sound it produces. So a small instrument creates short-wavelength sounds, just as a large instrument creates long-wavelength sounds.

Most of us have excellent relative pitch, which means that we can tell whether one sound has a different frequency from another. We can usually distinguish one sound from another if the frequencies of the two sounds differ by as little as 1 Hz. For example, Musical notes are particular sounds that can be produced by most instruments, and are the building blocks of a song. In Western music, musical notes have particular names, such as A-sharp, C, or E-flat.

Some people can identify musical notes just by listening to them. This rare ability is called perfect , or absolute, pitch. When a violin plays middle C, there is no mistaking it for a piano playing the same note. The reason is that each instrument produces a distinctive set of frequencies and intensities. We call our perception of these combinations of frequencies and intensities the timbre of the sound.

It is more difficult to quantify timbre than loudness or pitch. Timbre is more subjective. Evocative adjectives such as dull, brilliant, warm, cold, pure, and rich are used to describe the timbre of a sound rather than quantities with units, which makes for a difficult topic to dissect with physics.

So the consideration of timbre takes us into the realm of perceptual psychology, where higher-level processes in the brain are dominant. This is also true for other perceptions of sound, such as music and noise.

If students are struggling with a specific objective, these questions will help identify which and direct students to the relevant content. Nave, R. Vocal sound production—HyperPhysics. As an Amazon Associate we earn from qualifying purchases. Want to cite, share, or modify this book? This book is Creative Commons Attribution License 4. Changes were made to the original material, including updates to art, structure, and other content updates.

Skip to Content Go to accessibility page. Physics My highlights. Table of contents. Chapter Review. Test Prep. By the end of this section, you will be able to do the following: Relate amplitude of a wave to loudness and energy of a sound wave Describe the decibel scale for measuring sound intensity Solve problems involving the intensity of a sound wave Describe how humans produce and hear sounds.

Teacher Support The learning objectives in this section will help your students master the following standards: 7 Science concepts. The student knows the characteristics and behavior of waves. The student is expected to: C compare characteristics and behaviors of transverse waves, including electromagnetic waves and the electromagnetic spectrum, and characteristics and behaviors of longitudinal waves, including sound waves; F describe the role of wave characteristics and behaviors in medical and industrial applications.

The sound is perceived as louder if the amplitude increases, and softer if the amplitude decreases. This is illustrated below. The amplitude of a wave is related to the amount of energy it carries. A high amplitude wave carries a large amount of energy; a low amplitude wave carries a small amount of energy. The average amount of energy passing through a unit area per unit of time in a specified direction is called the intensity of the wave.

As the amplitude of the sound wave increases, the intensity of the sound increases. Sounds with higher intensities are perceived to be louder.

Relative sound intensities are often given in units named decibels dB. Search for:. Home Science of Sound Sound What is sound? How do you characterize sounds? Amplitude Intensity Frequency Wavelength How are sounds made? What happens when sound pressures are large? Sound Movement How fast does sound travel? Why does sound get weaker as it travels? Sound Spreading Sound Absorption How does sound move?

Reflection Refraction Scattering Reverberation How does sound travel long distances? Sound Measurement How is sound measured?

What units are used to measure sound? How are sounds viewed and analyzed? A level expressed in terms of decibels is a statement of a ratio relationship between two values—not an absolute measurement. If we consider one amplitude as a reference which we call A 0 , then the relative amplitude of another sound in decibels can be calculated with the equation:. If we consider the maximum possible amplitude as a reference with a numerical value of 1, then a sound with amplitude 0.

Each halving of amplitude is a difference of about -6 dB; each doubling of amplitude is an increase of about 6 dB. So, if one amplitude is 48 dB greater than another, one can estimate that it's about 2 to the 8th power times as great. Amplitude, Intensity, and Loudness Sound is variation in air pressure detectable by the human ear.

Intensity - Amplitude :. What is the formula of intensity? Intensity is defined to be the power per unit area carried by a wave. Power is the rate at which energy is transferred by the wave. How is amplitude measured? Amplitude is generally calculated by looking on a graph of a wave and measuring the height of the wave from the resting position.

The amplitude is a measure of the strength or intensity of the wave. For example, when looking at a sound wave, the amplitude will measure the loudness of the sound. What is the relationship between frequency and intensity? In the quantum mechanical view of light, if the photons per area and second are constant, then the intensity is directly proportional to the frequency in concordance with the photoelectric effect.

However, in a classical view the intensity of a field depends just on the amplitude, not its' frequency. How do you measure sound intensity? Physics Tutorial - Sound - Decibel Levels Find the ratio of the sound intensity to the threshold intensity. Take the logarithm of the ratio. Multiply the ratio by