# Audio Engineering MCQ Questions and Answers – Characteristics and Types of Loudspeaker – 1

This set of Audio Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Characteristics and Types of Loudspeaker – 1”.

1. Which of the following is also called reverse transducer?
a) Loudspeaker
b) Microphone
c) Baffle
d) Compact disk

Explanation: Loudspeaker is very important device present in any audio and video system such as public address systems, radios, televisions etc. Loudspeaker is a transducer which performs the reverse task of microphone. Hence it is also called a reverse transducer.

2. What is expressed as the ratio of output sound power to the input audio (electrical power) in loudspeaker?
a) Efficiency
b) Frequency response
c) Noise
d) Distortion

Explanation: Efficiency is defined as the ratio of output sound power to the input audio (electrical power). Efficiency is quoted in terms of sensitivity. Thus,
Efficiency = output sound power / input audio

3. What is expressed as the ratio of ‘signal output’ to the ‘output in the absence of signal’?
a) Distortion
b) Signal to noise ratio (S/N)
c) Directivity
d) Impedance

Explanation: Noise is any unwanted sound, not contained in the input signal but present in the output of the loudspeaker. Signal to noise ratio (S/N) is defined as the ratio of ‘signal output’ to the ‘output in the absence of signal’.

4. What is the unit for directivity in loudspeaker?
a) Hz
b) KHz
c) Decibel
d) Newton

Explanation: Directivity can be determined by the ratio of actual sound intensity at a point in the directions of maximum intensity to the sound intensity. Directivity is a measure of the directional characteristic of a sound source. It is often expressed in decibels.

5. On which principle is the moving-coil loudspeaker based?
a) Electromagnetic transduction
b) Electromagnetic induction
c) Piezoelectric effect
d) Electro dynamic induction

Explanation: The moving coil loudspeaker is based on the principle of electromagnetic transduction. It is the exact reverse process of the process involved in the moving coil microphone. A coil called voice coil is placed in a uniform magnetic field. When audio current passes through the voice coil, there is an interaction between the magnetic field and the coil, which will result in a force working on the movable coil.
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6. What is the equation for the force in newton on the coil due to interaction between current through the coil and magnitude field?
a) F = Bli sin α
b) F = Bli tan α
c) F = Bli cos α
d) F = Bl sin α

Explanation: The force in newton on the coil due to interaction between current through the coil and magnitude field is given by the equation, F = Bli sin α
Where,
F = force in newton, B = flux density in Wb/m2, l = length of coil wire in meter, i = current in ampere, α = angle between the coil and the field.

7. Which magnetic material is the magnet in the moving coil loudspeaker made up of?
a) AlNiCo
b) BrNiCo
c) XeNiCo
d) PNiCo

Explanation: The magnet in the moving coil loudspeaker is made up of high grade magnetic material like AlNiCo (composition of Aluminium 18%, Nickel 10%, Cobalt 12%, Copper 6% and Iron 54%) which returns the magnetism extremely well.

8. What is attached to the coil of moving coil loudspeaker and it causes compression and rarefaction cycles in air?
a) Paper cone
b) Electrodynamic
c) Horn
d) Ribbon

Explanation: When audio current is passed through the voice coil placed in a magnetic field, a generated force equal to Bli Newton acts on the coil and move it to and fro. The paper cone attached to the coil also moves and causes compression and rarefaction cycles in the air. Thus, audio current is finally converted into sound waves.

9. The efficiency of cone speaker is very low about 5 to 10 percent only.
a) True
b) False

Explanation: The efficiency of a cone speaker is very low about 5 to 10% only. The poor efficiency is due to the reason that loudspeaker acts as a direct radiator and so there is complete mismatch between the lower acoustic load presented by the large volume of air and high mechanical load presented by the voice coil and cone assembly.

10. What is the power handling capacity for cone type speaker?
a) Up to 25 watts
b) Up to 250 watts
c) Up to 235 watts
d) Up to 75 watts

Explanation: The cone type speaker is also called as direct radiating type loudspeaker. The power handling capacity of cone type speaker is up to 25 watts for normal and up to 1000 watts for electro dynamic speaker.

11. Cone type microphone is used in radios, TVs, music systems and mobiles.
a) True
b) False

Explanation: The size and cost of cone type speaker is low and the directivity is also good. The diaphragm is extended in the form of paper cone. So, cone type microphone is used in radios, TVs, music systems and mobiles.

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