Contoh Soal & Latihan Gelombang Bunyi | Intensitas dan Taraf Intensitas Bunyi (Fisika Kelas 11)

Introduction

This tutorial will guide you through the concepts of sound waves, intensity, and sound intensity level as discussed in the video "Contoh Soal & Latihan Gelombang Bunyi | Intensitas dan Taraf Intensitas Bunyi" by Ni'matullah. You will learn how to calculate the sound intensity level from multiple sound sources and understand the fundamental principles of sound waves as part of your 11th-grade physics curriculum.

Step 1: Understanding Sound Waves

• Definition: Sound waves are vibrations that travel through a medium (like air, water, or solids) and can be heard when they reach a person's or animal's ear.
• Properties:
  • Frequency: Determines the pitch of the sound (measured in Hertz).
  • Wavelength: The distance between successive peaks of a wave.
  • Amplitude: Relates to the loudness of the sound.

Practical Tip

• Use a tuning fork or a smartphone app to visualize sound waves and their properties.

Step 2: Exploring Sound Intensity

• Definition: Sound intensity is the power per unit area carried by a sound wave, typically measured in watts per square meter (W/m²).
• Formula:
  • Intensity (I) = Power (P) / Area (A)

Common Pitfalls

• Confusing intensity with loudness; loudness is a subjective perception while intensity is a measurable quantity.

Step 3: Understanding Sound Intensity Level

• Definition: Sound intensity level is a logarithmic measure of the intensity of sound relative to a reference level, often denoted in decibels (dB).
• Formula:
  • ( L = 10 \cdot \log_{10} \left( \frac{I}{I_0} \right) )
  • Where ( L ) is the sound intensity level in decibels, ( I ) is the sound intensity, and ( I_0 ) is the reference intensity (typically ( 1 \times 10^{-12} ) W/m²).

Practical Application

• Use this formula to compare the intensity of different sounds, such as a whisper versus a rock concert.

Step 4: Calculating Combined Sound Intensity Levels

• When multiple sound sources are present, you can calculate the total intensity level using:
  • Convert each sound intensity level from dB back to intensity using the formula above.
  • Sum all the intensities.
  • Convert the total intensity back to dB using the sound intensity level formula.

Example Calculation

1. Calculate the intensity levels for two sources:
   • Source 1: ( 70 ) dB
   • Source 2: ( 75 ) dB
2. Convert both to intensity:
   • Source 1: ( I_1 = 1 \times 10^{-12} \cdot 10^{(70/10)} )
   • Source 2: ( I_2 = 1 \times 10^{-12} \cdot 10^{(75/10)} )
3. Sum intensities: ( I_{total} = I_1 + I_2 )
4. Convert back to dB: ( L_{total} = 10 \cdot \log_{10} \left( \frac{I_{total}}{I_0} \right) )

Step 5: Practice Problems

• Work through sample problems presented in the video to reinforce the concepts.
• Example Problem: If two sound sources have intensities of ( 0.01 , W/m² ) and ( 0.1 , W/m² ), calculate the combined sound intensity level.

Practical Tip

• Use online calculators for logarithmic functions to verify your calculations.

Conclusion

In this tutorial, you have learned about sound waves, intensity, and how to calculate sound intensity levels. Understanding these concepts is essential for tackling problems in your physics class and applying them in real-world situations. Next, try solving additional practice problems or explore related topics, such as the Doppler effect or sound wave applications in technology.