Sound

Equipment Used: Signal generator and loudspeakers.
Observations: Walking from point A to B affects loudness, showing intervals of increasing and decreasing sound.
Explanation: This phenomenon occurs due to constructive (amplifying) and destructive (diminishing) interference of sound waves from two speakers along path AB.

Basic Principle: The frequency of the vibrating source matches the frequency of the surrounding vibrating molecules, thus the sound wave frequency equals that of the vibrating source.

Vacuum Experiment:
- Set up a bell jar and observe the bell ringing initially.
- As air is evacuated using a vacuum pump, the sound becomes progressively quieter until inaudible.
Conclusion: Sound requires a medium (e.g., air) to propagate; without it, sound does not travel.

Definition: The natural frequency is the resonating frequency of an object when it vibrates freely.
Determining Factors of Natural Frequency of a Stretched String:
1. Length of String: Frequency is inversely proportional to the length (f ∝ 1/L).
2. Tension in String: Frequency is directly proportional to the square root of tension (f ∝ √T).
3. Mass per Unit Length: Frequency is inversely proportional to the square root of mass per unit length (f ∝ 1/√µ).

Formula Reference: If T = tension, u = mass per unit length, I = length, and f = fundamental frequency, the relationships are established as:
- With T and μ fixed: f ∝ √(T/I)
- With I and u fixed: f ∝ (√T)
- With μ and I fixed: f = k • 1/√L (where k is a constant).

Definition: Resonance involves energy transfer causing an object to vibrate at its natural frequency.
Demonstration: Using two identical tuning forks, if one is started and placed on a soundboard, it will cause the second fork to vibrate and sound, despite stopping the first.
Examples: Resonance can lead to structural damage during earthquakes if the earthquake's frequency matches a building's natural frequency.

Definition: Sound intensity is the power transmitted per unit area (measured in W/m²).
Characteristics: Sound energy spreads uniformly in all directions, akin to a balloon inflating, covering the surface area of a sphere (4πr²).

Description: The threshold of hearing is the minimal sound intensity observable by the human ear, positioned at a frequency of 1000 Hz (D 1 x 10^-12 W/m²).
Decibel Scale: Sound intensity is quantified in decibels (dB), creating a logarithmic intensity scale detailing hearing capacity from 10^-12 W/m² to 1 W/m².

Purpose: Modified for the ear's frequency response, as humans are more sensitive between 2000 Hz and 4000 Hz.

General Principle: Sound travels fastest in solids, followed by liquids, and slowest in gases.
Speed in Air: At 20°C, the speed of sound in air is approximately 343 m/s.

Harmonics: Frequencies that are integer multiples of the fundamental frequency (f).
Overtones: Frequencies that are multiples of a given frequency (e.g., 2f is the first overtone).

Procedure:
1. Strike a tuning fork and position it over a resonance tube.
2. Adjust the tube to find the loudest resonance sound, measuring the distance corresponding to approximately a quarter wavelength.
3. Note the frequency of the tuning fork, and calculate wavelength using c = 4f(l + 0.3d).

Setup: Use a sonometer to fix tension constant and measure length, adjusting frequency until resonance is achieved.
Data Recording: Plot frequency versus 1/length, verifying frequency's inverse relationship to length through a linear graph originating from zero.

Experimental Design: Fix wire length and adjust tension, measuring frequency at each step.
Graphical Analysis: Frequency plotted against the square root of tension should yield a straight line, affirming that frequency is proportional to the square root of tension.