Which of the following waves are audible to humans?

Explanation / व्याख्या
Human beings can hear sound waves only within a specific frequency range known as the audible range. This range is approximately from 20 Hz to 20,000 Hz (20 kHz). Sounds below 20 Hz are called infrasound, and above 20,000 Hz are called ultrasound, both of which are not audible to humans.

मनुष्य केवल एक निश्चित आवृत्ति सीमा की ध्वनि तरंगों को सुन सकता है, जिसे श्रव्य सीमा (audible range) कहा जाता है। यह सीमा लगभग 20 Hz से 20,000 Hz (20 kHz) तक होती है। 20 Hz से कम को अवश्रव्य (infrasound) और 20,000 Hz से अधिक को पराश्रव्य (ultrasound) कहते हैं, जिन्हें मनुष्य नहीं सुन सकता।

Key Facts / महत्वपूर्ण तथ्य

• 👂 Normal human hearing range: 20 Hz – 20 kHz
• 🔉 Dogs can hear higher frequencies than humans
• 🐘 Elephants can produce infrasound (<20 Hz)
• 🧪 Ultrasound is used in medical imaging (like sonography)

❌ Why others are incorrect / अन्य विकल्प क्यों गलत हैं

• Less than 20 Hz: Infrasound (not audible)
• 20 Hz to 2000 Hz: Too narrow; humans hear much higher
• More than 2000 Hz: Only partial range; excludes lower audible sounds