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Fundamentals of Acoustics

Fundamentals of Acoustics. Instructor: Prof. Nachiketa Tiwari, Department of Mechanical Engineering, IIT Kanpur. This course provides the basics of acoustics, and covers topics in the field: the nature of sound, sound terminology, overview of some important mathematical concepts like complex algebra and complex time signals, wave equation, sound propagation in a tube, acoustic power, spherical waves, interference of sound sources, noise reduction by mass attenuation, designing mufflers, Fourier series and (Fast) Fourier Transforms, microphones, weighting, loudness, octave band analysis, reverberation time, sound transmission class, and noise reduction coefficient. (from nptel.ac.in)

Lecture 06 - Adding Decibels

This lecture covers the following topics: How to add decibels of two different sources - correlated and uncorrelated signals.

Go to the Course Home or watch other lectures:

Introduction and Terminology

Lecture 01 - Course Overview

Lecture 02 - Introduction

Lecture 03 - Nature of Sound

Lecture 04 - The Decibel Scale

Lecture 05 - Key Terms in Acoustics

Lecture 06 - Adding Decibels

Concept Review

Lecture 07 - Important Mathematical Concepts - Complex Algebra

Lecture 08 - Important Mathematical Concepts - Complex Time Signals

Lecture 09 - Important Mathematical Concepts - Transfer Function

Lecture 10 - Important Mathematical Concepts - Pole Zero Plot

Lecture 11 - Important Mathematical Concepts - Bode Plot for Simple Pole

Lecture 12 - Important Mathematical Concepts - Bode Plot for Simple Zero

Wave Equation

Lecture 13 - Bode Plots (Magnitude) for Complex Transfer Functions

Lecture 14 - Momentum Equation for 1-D Sound Propagation

Lecture 15 - Continuity Equation for 1-D Sound Propagation

Lecture 16 - Gas Law for 1-D Sound Propagation

Lecture 17 - 1-D Sound Wave Equation

Lecture 18 - Solution for 1-D Sound Wave Equation

Transmission Line Equations

Lecture 19 - Waveguide

Lecture 20 - Sound Propagation in a Semi-Infinite Tube

Lecture 21 - Transmission Line Equations for Pressure and Velocity

Lecture 22 - Sound Propagation in a Closed Tube

Lecture 23 - Sound Propagation in Closed Tubes

Lecture 24 - Sound Propagation in a Open Tube

1-D Waves

Lecture 25 - Instantaneous Power

Lecture 26 - Instantaneous Power in a L-R Circuit

Lecture 27 - Power Factor, and Acoustic Power

Lecture 28 - Power Flow into an Infinitely Long Tube

Lecture 29 - Point Sources of Sound

Lecture 30 - Relations for Outward Travelling Spherical Acoustic Wave

Power and Spherical Waves

Lecture 31 - Specific Acoustic Impedance for a Closed Tube

Lecture 32 - Specific Acoustic Impedance for an Open Tube and an Infinitely Long Tube

Lecture 33 - Specific Acoustic Impedance for a Tube with Imperfect Termination

Lecture 34 - Kundt's Tube

Lecture 35 - Volume Velocity

Lecture 36 - Comparison of Impedances for a Radially Propagating Wave and a Planar Wave

Spherical Waves and Interference

Lecture 37 - Interference of Two Sound Sources

Lecture 38 - Interference of Two Sound Sources with Zero Phase Difference

Lecture 39 - Interference of Four Sound Sources with Zero Phase Difference

Lecture 40 - Interference of n-Sound Sources with Zero Phase Difference

Lecture 41 - Directivity Pattern, Directivity Factor, Directivity Index

Lecture 42 - Complex Power, Pressure and Velocity for a Spherical Source

Directivity and Mufflers

Lecture 43 - Noise Reduction by Mass Attenuation

Lecture 44 - Noise Reduction - Pressure Ratio

Lecture 45 - Noise Reduction - Velocity of Wall

Lecture 46 - 3 Media Problem - Introduction

Lecture 47 - 3 Media Problem - Applying Boundary Conditions

Lecture 48 - 3 Media Problem - Special Cases

Sound in Rooms

Lecture 49 - Mufflers

Lecture 50 - Designing of Reactive Mufflers

Lecture 51 - Designing of Dissipative Mufflers

Lecture 52 - Time and Frequency Domain Representation of a Signal

Lecture 53 - Fourier Series

Lecture 54 - Fourier Series (cont.)

Fourier Transform, DFT and FFT

Lecture 55 - Fourier Transform

Lecture 56 - Fourier Transform (cont.)

Lecture 57 - Fourier Transform (cont.)

Lecture 58 - Discrete Fourier Transform (DFT)

Lecture 59 - Discrete Fourier Transform (cont.)

Lecture 60 - Discrete Fourier Transform (cont.)

Weighting and Loudness

Lecture 61 - Measuring Sound Signals

Lecture 62 - Microphones

Lecture 63 - Classification of Microphones based on Application

Lecture 64 - Weighting

Lecture 65 - Loudness

Lecture 66 - Loudness (cont.)

Miscellaneous Topics and Closure

Lecture 67 - Octave Band Analysis, Part I

Lecture 68 - Octave Band Analysis, Part II

Lecture 69 - Octave Band Analysis: Plotting Octave Band Plots

Lecture 70 - Reverberation Time

Lecture 71 - Calculation of Reverberation Time and Sound Transmission Class (STC)

Lecture 72 - Noise Reduction Coefficient (NRC)