Loudness of sound is discriminated by

Options

A. Intensity of movement of basilar fibres of cochlea
B. Vibration of semicircular canals
C. Vibration of end lymphatic sac
D. Vibration of tympanic bulla

Explanation

### Step-by-Step Solution:

1. **Understand the Concept of Loudness**: Loudness of sound is primarily determined by the intensity of sound waves. It is a perceptual response to the physical characteristics of sound.

2. **Identify the Role of the Basilar Membrane**: The basilar membrane is a key structure in the cochlea of the inner ear. It plays a crucial role in the auditory system by responding to different frequencies of sound.

3. **Movement of Basilar Fibers**: When sound waves enter the ear, they cause the basilar membrane to vibrate. The intensity of these vibrations correlates with the loudness of the sound. More intense sounds cause greater movement of the basilar fibers.

4. **Comparison with Other Structures**: The question provides several options regarding structures involved in sound discrimination. However, the primary structure responsible for discriminating loudness is the basilar membrane, specifically the intensity of movement of its fibers.

5. **Conclusion**: Based on the understanding that the loudness of sound is discriminated by the intensity of the movement of the basilar fibers of the cochlea, the correct answer to the question is option A.

### Final Answer:
The loudness of sound is discriminated by the intensity of movement of basilar fibers of the cochlea.

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