This set of Audio Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Sound Characteristics – Helmholtz Resonator”.
1. Which resonator is a container/bottle of gas with an open hole?
a) Helmholtz
b) Coaxial
c) Dielectric
d) Crystal
View Answer
Explanation: A Helmholtz resonator or oscillator is a container/bottle of gas (generally air) with an open hole (neck or port). A volume of air in and near the open hole vibrates because of the ‘springiness’ of the air inside. A common example is an empty bottle and gastropod sea-shell.
2. The air in the body of a guitar acts like a Helmholtz resonator.
a) True
b) False
View Answer
Explanation: Almost all small whistles are Helmholtz oscillator. The air in the body of a guitar acts like a Helmholtz resonator. Loud speaker enclosures often use the Helmholtz resonance of the enclosure to boost the low frequency response.
3. By which formula the resonant frequency is determined?
a) f = c/2π√B/VS Hz
b) f = c/5π√A/VL Hz
c) f = c/2π√A/VL Hz
d) f = c/3π√A/VS Hz
View Answer
Explanation: The resonant frequency is determined by the formula:
f = c/2π√A/VL Hz.
Where, f = frequency in hertz, c = the speed of sound in air, A = Area of the cross-section of the neck, L = Length of the neck, V = Volume of the enclosure.
4. Which resonant frequencies can be obtained with Helmholtz resonator?
a) Low
b) High
c) Medium
d) Low and High
View Answer
Explanation: Helmholtz resonator has many applications. Low resonant frequencies can be obtained with Helmholtz resonators of relatively small size. Subwoofers are a key part in producing low frequencies in surround sound systems, concerts etc.
5. Which is one of the most common applications of Helmholtz resonator?
a) Woofer
b) Subwoofer
c) Reflection
d) Diffraction
View Answer
Explanation: One of the most common applications of Helmholtz resonators is in subwoofers. Subwoofers were developed to add bass response to home stereo systems. There are different types of subwoofers that use different designs to accomplish the same purpose. These include bass reflex, infinite baffle, horn loaded and band pass.
6. In which instruments Helmholtz resonators also important?
a) Stringed
b) Woodwind
c) Brass
d) Keyboard
View Answer
Explanation: Helmholtz resonance is also important in stringed instruments. Guitars and violins are Helmholtz resonators that use the vibration of the resonator along with the vibrations of the wooden bodies.
7. The vibration in the Helmholtz oscillator is due to the ‘springiness’ of air.
a) True
b) False
View Answer
Explanation: The above statement is false. The vibration in the Helmholtz resonator is due to the ‘springiness’ of air. When you compress it, its pressure increases and it tends to expand back to its original volume.
8. What is disturbed at the opening of Helmholtz resonator that bounces like a mass on a spring in simple harmonic motion which creates sound?
a) Air
b) Water
c) Sound
d) Frequency
View Answer
Explanation: When the air in the opening of a Helmholtz resonator is disturbed, it bounces like a mass on spring in simple harmonic motion, creating sound. The frequency of the sound created is equal to that of the air’s vibration.
Sanfoundry Global Education & Learning Series – Audio Engineering.
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