Give reasons why audio frequency signal cannot transmitted directly without carrier signal.

1. Limited Transmission Range:
- Audio signals have relatively low frequencies (20 Hz - 20 kHz) and weak energy, making their transmission range very limited.
- Without a carrier signal, the audio signals would quickly dissipate in the atmosphere, resulting in poor reach.

2. Lower Power Efficiency:
- Transmitting audio signals directly would require very high power to achieve the same coverage as modulated signals.
- Combining audio signals with a higher frequency carrier signal allows for higher power efficiency and extended transmission range.

3. Interference and Noise Susceptibility:
- Audio signals are highly susceptible to interference from other sources, such as electrical noise and electromagnetic radiation.
- Carrier signals act as a shield, helping to minimize interference and improve signal quality.

4. Limited Channel Capacity:
- Direct transmission of audio signals would require multiple frequencies to accommodate the full range of frequencies (20 Hz - 20 kHz).
- Modulation onto a carrier signal allows multiple audio signals to be transmitted on the same frequency, increasing channel capacity.

5. Antenna Size Constraint:
- The wavelength of audio signals is very long, requiring large antennas for efficient transmission.
- Modulating the audio signal onto a higher frequency carrier reduces the wavelength, enabling the use of smaller, more practical antennas.

6. Frequency Allocation and Regulations:
- Radio frequency spectrum is divided into different frequency bands with specific allocations.
- Audio frequencies are not typically assigned for direct transmission, and using a carrier signal allows compliance with regulations.

7. Multiple Access and Synchronization:
- In wireless communications, multiple devices may need to transmit simultaneously.
- Carrier modulation allows for synchronization and multiplexing of multiple signals, enabling efficient use of the available spectrum.