Abstract: A volume control method. An audio device. A portable communication system. First, an audio signal is input. At least one environmental noise is detected. An output gain is then determined based on the environmental noise, and the audio signal is amplified based thereon. The environmental noise comprises noises from various directions and various positions, and the output gain is proportional to the amplitude of the environmental noise. A custom gain is further received, and a sound pressure level (SPL) of the environmental noise is calculated. Therefore the output gain can be determined by summing the sound pressure level and the custom gain.