Gelombang Bunyi • Part 6: Efek Doppler

Summary

This video explains the Doppler Effect, a phenomenon where the frequency of sound heard by an observer differs from the original frequency due to the relative motion of the source and the observer. Using everyday examples, such as the sound of a horn from a moving vehicle, the video illustrates how the pitch changes as the source moves toward or away from the listener. The presenter also provides calculations to demonstrate how speed and direction of movement, as well as wind, influence the perceived frequency. The video includes practical examples and step-by-step problem-solving.

Takeaways

• 😀 Doppler Effect occurs when an observer hears a frequency different from the original frequency emitted by a sound source.
• 😀 The frequency of sound can increase or decrease depending on whether the sound source or the observer is moving toward or away from each other.
• 😀 The Doppler Effect is noticeable in everyday life, such as hearing the change in sound frequency as an ambulance or car passes by.
• 😀 When a sound source moves toward the observer, the observed frequency is higher. When it moves away, the observed frequency is lower.
• 😀 The speed of sound in air is typically around 340 meters per second but may vary based on conditions like temperature or pressure.
• 😀 The formula for the Doppler Effect involves variables such as the speed of sound, speed of the observer, and the speed of the source.
• 😀 In the formula, the observer's speed (VP) is positive when they are moving toward the source and negative when moving away.
• 😀 The source's speed (VS) is positive when the source is moving away from the observer and negative when approaching the observer.
• 😀 The wind's speed (VA) can either aid or hinder the sound's transmission, depending on the direction of the wind relative to the observer and source.
• 😀 An example problem involves calculating the frequency heard by an observer when a vehicle or sound source is moving toward or away from them, factoring in the relative speeds and the speed of sound.

Q & A

What is the Doppler Effect?

The Doppler Effect is a phenomenon where the frequency of sound perceived by an observer is different from the frequency emitted by the source due to the relative motion between the source and the observer.

How does the Doppler Effect manifest in everyday life?

The Doppler Effect can be observed when a vehicle, like a car or ambulance, honks its horn while moving. As the vehicle approaches the observer, the sound's frequency appears higher, and as it moves away, the frequency appears lower.

What happens to the perceived frequency when the sound source and observer are moving towards each other?

When both the source and observer move towards each other, the perceived frequency increases. This is because the sound waves are compressed, leading to a higher frequency.

What changes occur to the perceived frequency when the sound source and observer move apart?

When the sound source and observer move away from each other, the perceived frequency decreases. This is because the sound waves are stretched out, resulting in a lower frequency.

What does the equation for Doppler Effect represent?

The Doppler Effect equation represents the relationship between the observed frequency, the speed of sound, and the relative speeds of the source and observer. It accounts for the movement of the source, observer, and wind.

What does the variable 'V' in the Doppler Effect equation represent?

In the Doppler Effect equation, 'V' represents the speed of sound in air, typically 340 meters per second, although it can vary depending on conditions like temperature and pressure.

How do you determine whether the velocity values are positive or negative in the Doppler Effect formula?

The velocity values in the Doppler Effect formula are positive when the observer or source is moving towards each other and negative when they are moving away from each other. If either is stationary, the velocity is set to zero.

In the example of a car and bus honking a horn, how does the perceived frequency change before and after they pass each other?

Before passing, the observed frequency is higher as the car and bus approach each other. After they pass, the observed frequency decreases as the car and bus move away from each other.

How does wind influence the Doppler Effect?

Wind can affect the Doppler Effect by altering the speed at which sound waves travel. If the wind blows from the source to the observer, it increases the sound's speed, leading to a higher perceived frequency. If the wind blows the other way, it decreases the sound's speed, leading to a lower perceived frequency.

In a scenario where a motorbike moves towards a train and sound travels with the wind, how do the velocities of the motorbike and train affect the perceived frequency?

When the motorbike moves towards the train while the wind helps the sound travel from the train to the motorbike, the motorbike perceives a higher frequency. The wind accelerates sound waves, increasing the perceived frequency due to the combined motion of the motorbike and the wind.