Contextualization

Sound intensity is a quantity that measures the amount of sound energy passing through an area per unit of time. It is directly related to our perception of what we consider as the sound 'volume'. Sound intensity is directly proportional to the amplitude of the sound wave and is measured in decibels (dB).

Sound intensity can vary in a complex way with frequency and direction, besides being directly affected by obstacles present in the environment. Furthermore, sound has the characteristic of propagating in different mediums (gas, liquid, or solid), altering its speed and intensity in the process.

To measure sound intensity, it is necessary to first understand the nature of sound as a type of mechanical energy that propagates through pressure waves. The relationship between sound intensity and sound pressure is expressed by the following formula: I = p² / (2ρv), where I is the sound intensity, p is the sound pressure, ρ is the medium density, and v is the speed of sound in the medium.

Importance of the Theme

In our daily lives, we are constantly exposed to different sound intensities. Whether it's traffic noise, music through headphones, or the sound of a conversation. Understanding sound intensity is crucial to comprehend how to protect our hearing, design the acoustics of buildings and concert halls, and even how sound pollution can affect the environment.

Moreover, in areas such as acoustic engineering, physics, and audiology, the study of sound intensity is fundamental. Professionals in these fields need to understand and calculate sound intensity to design rooms with proper acoustics, protect hearing in noisy work environments, and evaluate the quality of audio equipment.

Practical Activity: 'Sound Intensity: From Theory to Practice'

Project Objective

The objective of this project is to study sound intensity: understand what it is, how to calculate it, how to measure it, and its real-world applications. The project will have a practical focus where students will conduct experiments related to sound propagation and the influence of propagation mediums on sound.

Students should work in groups of 3 to 5, and the project should take more than twelve hours of work per student to complete. More than four topics will be investigated, including key concepts such as sound pressure, sound power, sound power density, sound intensity, decibel, Doppler effect, and the effect of temperature and propagation medium on sound.

The project will cross disciplinary boundaries, covering both Physics and Mathematics, as students will need to apply mathematical concepts to solve the proposed problems.

Project Description

Students will conduct various experiments to measure sound intensity using a decibel meter app available for smartphones. Additionally, they will be challenged to investigate how the distance from the sound source and different obstacles in the path of the sound wave affect the perceived sound intensity.

Required Materials

• Safety glasses
• Smartphone or tablet with a decibel meter app installed
• Headphones
• Sound source (e.g., musical instrument, speaker, etc.)
• Tape measure
• Various materials to serve as obstacles (e.g., walls of different thicknesses, cloths, curtains, glass, etc.)
• Notebook for notes

Step by Step

1. Understanding the Theory: Students should first study the theory of sound intensity and related topics using the recommended resources. All group members should understand the concepts and be able to explain them.

2. Experiment Planning: The group should plan the experiments they will conduct, defining which variables they will manipulate (e.g., distance from the sound source, obstacles in the sound path, etc.), and how they will measure sound intensity in each case.

3. Experiment Execution: Conduct the experiments as planned, taking careful notes of all procedures, observations, and measurements.

4. Results Analysis: Analyze the collected data. Use graphs and mathematical calculations to understand the relationships between the variables.

5. Final Report: Write a detailed report on the project, including all specified parts: Introduction, Development, Conclusions, and Bibliography.

Project Delivery

At the end of the project, each group must deliver:

1. Written Report: This document should contain an introduction (contextualizing the theme, its relevance, real-world applications, and the project's objective), development (explaining the theory, detailing the activity, indicating the methodology used, and presenting and discussing the results obtained), conclusions (summarizing the main points, explaining the learnings obtained, and drawing conclusions about the project), and the bibliography used.

2. Oral Presentation: Each group must prepare a brief oral presentation of their results for the class, focusing mainly on the procedures carried out and the conclusions drawn.

Students should strive for the written report and the oral presentation to complement each other, each providing different parts of a cohesive narrative about the work done.

Furthermore, by conducting this project, it is expected that students will acquire technical skills such as understanding and calculating sound intensity, as well as socio-emotional skills such as time management, communication, problem-solving, creative thinking, proactivity, etc.