Gelombang Bunyi • Part 7: Intensitas Bunyi dan Taraf Intensitas Bunyi

Summary

In this educational video, the channel delves into the concepts of sound waves, focusing on sound intensity and its measurement. The explanation covers the formula for sound intensity, how it relates to energy propagation through waves, and the relationship between intensity and distance from the sound source. The video also introduces the concept of intensity level (in decibels) and provides formulas for calculating intensity at different distances. Using a real-world example, the video demonstrates how to calculate the intensity and intensity level of sound at a specific distance, providing a clear and practical understanding of the topic.

Takeaways

• 😀 Intensitas bunyi (sound intensity) is calculated as P / A, where P is the power (in watts) and A is the surface area (in m²) through which the sound energy passes.
• 😀 The sound wave propagates in all directions, and its energy spreads out over a spherical surface. The formula for the surface area of this sphere is 4πr², where r is the distance from the source.
• 😀 The intensity level formula (TII) is 10 log(I/I₀), where I is the sound intensity and I₀ is the threshold intensity (10⁻¹² W/m²), the smallest sound intensity that the human ear can detect.
• 😀 The intensity of sound varies with distance from the source, and the relationship is given by I₁/I₂ = (R₁/R₂)², where I₁ and I₂ are the sound intensities at distances R₁ and R₂ from the source, respectively.
• 😀 Sound intensity levels at different distances can be related using the formula T₂ = T₁ + 20 log(R₁/R₂), where T₁ and T₂ are the intensity levels in decibels at distances R₁ and R₂.
• 😀 For multiple identical sound sources, the total intensity is the sum of the intensities from each source, and the total intensity level increases by 10 log(n), where n is the number of sources.
• 😀 The logarithmic properties of sound intensity include: log(A × B) = log(A) + log(B), and log(A / B) = log(A) - log(B). These rules are essential for solving intensity-related problems.
• 😀 Sound intensity can be used to assess noise levels in various environments. Loud locations tend to have higher intensity, while quieter locations have lower intensity.
• 😀 In real-world applications, measuring the intensity and intensity level of sound helps in understanding the noise pollution in various settings such as factories, concerts, and public spaces.
• 😀 A practical example is provided, where a sound source with a power of 640 W is used to calculate the intensity and intensity level at a distance of 4 meters. The intensity is 10 W/m², and the intensity level is 130 dB.

Q & A

What is the formula for sound intensity?

The formula for sound intensity is I = P / A, where 'I' is the sound intensity in watts per square meter (W/m²), 'P' is the power in watts (W), and 'A' is the area in square meters (m²) through which the sound is passing.

Why is the sound intensity formula related to the power and area?

Sound intensity is related to power and area because sound is a wave that carries energy. The power (P) represents the energy transferred per unit of time, while the area (A) represents the space through which the sound is propagating. Therefore, intensity is the amount of energy passing through a unit area per unit time.

What is the significance of 4πr² in the intensity formula?

The term 4πr² appears because sound waves spread out uniformly in all directions. The surface area of a sphere is given by 4πr², where 'r' is the radius. Since sound propagates in all directions, the area through which the sound energy passes is spherical, and this term accounts for that.

What is the threshold intensity of hearing for the human ear?

The threshold intensity of hearing for the human ear is typically 10^-12 W/m². This is the smallest intensity of sound that the average human ear can detect.

How is sound intensity level (SIL) related to sound intensity?

Sound intensity level (SIL) is a logarithmic measure of sound intensity. The formula for SIL is L = 10 * log10(I / I₀), where 'L' is the sound intensity level in decibels (dB), 'I' is the sound intensity in W/m², and 'I₀' is the reference intensity (the threshold of hearing, typically 10^-12 W/m²).

How does sound intensity change with distance from the source?

As sound travels away from the source, the intensity decreases with the square of the distance. The formula I1/I2 = (R2/R1)² expresses this relationship, where I1 and I2 are the sound intensities at distances R1 and R2 from the source, respectively.

What is the relationship between sound intensity levels at different distances?

The sound intensity level (SIL) at different distances is related by the formula T2 = T1 + 20 * log10(R1/R2), where T1 and T2 are the sound intensity levels at distances R1 and R2, respectively. This formula shows how the SIL changes as the distance from the sound source changes.

What happens to sound intensity when multiple identical sound sources are added?

When multiple identical sound sources are combined, the total sound intensity is the sum of the individual intensities. For 'n' identical sources, the total intensity is given by I_total = n * I, where 'I' is the intensity of a single source.

How is the total sound intensity level calculated for multiple sources?

The total sound intensity level for multiple identical sources is calculated using the formula Tn = T + 10 * log10(n), where T is the intensity level of one source, and 'n' is the number of sources. This formula accounts for the increase in intensity due to the number of sources.

How do logarithmic properties help in simplifying sound intensity calculations?

Logarithmic properties allow for the simplification of calculations involving sound intensity, especially when dealing with multiplication or division of intensities. For example, the product of two intensities can be expressed as the sum of their logarithms, and the ratio of intensities can be expressed as the difference of their logarithms.