Telephone signals travel through wires at nearly the speed of light, making them much faster than the speed of sound.

Telephone communication relies on the conversion of acoustic sound waves into electromagnetic signals. When you speak into a phone, the microphone uses a diaphragm to convert sound pressure into electrical pulses. These pulses travel through copper wires as electrons or through fiber-optic cables as photons of light. In a vacuum, light travels at approximately 186,282 miles per second, which is about 300,000 kilometers per second.In physical cables, the signal speed is slightly slower due to the refractive index of the material, typically reaching 60% to 90% of the speed of light. For example, signals in fiber-optic cables move at roughly 124,000 miles per second. This is still significantly faster than the speed of sound in air, which is only about 0.21 miles per second at sea level. This massive difference explains why long-distance calls have negligible latency.The technology behind this dates back to Alexander Graham Bell's first successful transmission in 1876. Modern telecommunications have since evolved to use the Synchronous Optical Networking (SONET) standard to manage these high-speed data flows. Research from institutions like Bell Labs has consistently pushed the limits of signal integrity over thousands of miles. Today, undersea fiber-optic cables like the MAREA cable can transmit data at speeds exceeding 160 terabits per second across the Atlantic Ocean.