1.1 Audio Signal Terms, Vocabulary, & Sound Characteristics.pdf

Audio Signal Terms, Vocabulary, & Sound Characteristics What is audio signal An audio signal is a representation of sound waves that can be transmitted, recorded, and reproduced. => Time Amplitude Amplitude: The loudness of an audio signal, typica...

Audio Signal Terms, Vocabulary, & Sound Characteristics What is audio signal An audio signal is a representation of sound waves that can be transmitted, recorded, and reproduced. => Time Amplitude Amplitude: The loudness of an audio signal, typically measured in decibels (dB). Higher amplitude means louder sound. Frequency number of cycles per second. The unit of frequency is hertz Higher frequencies correspond to higher pitches, and lower frequencies correspond to lower pitches. Frequency Higher frequency  more cycle/s Fundamental Frequency The lowest frequency of any vibrating object is called the fundamental frequency. The fundamental frequency provides the sound with its strongest audible pitch reference - it is the predominant frequency in any complex waveform. Harmonics A harmonic is one of an ascending series of sonic components that sound above the audible fundamental frequency. The higher frequency harmonics that sound above the fundamental make up the harmonic spectrum of the sound Harmonics have a lower amplitude than the fundamental frequency. Harmonics are integer multiples of the fundamental frequency. For example, if the fundamental frequency is 50 Hz (also known as the first harmonic) then the second harmonic will be 100 Hz (50 * 2 = 100 Hz), the third harmonic will be 150 Hz (50 * 3 = 150 Hz), and so on. Harmonics can indicate distortion in a signal  Fundamental Frequency and Harmonics Fundamental Frequency Harmonics F0=1000 Hz F1=2000 Hz F2=3000 Hz F3=4000 Hz etc Overtones Overtones are frequencies of a waveform that are higher than, but not directly related to, the fundamental frequency. Timbre Timbre: The quality or color of a sound that allows us to differentiate between different sources, even when they play the same pitch. It is affected by harmonics and the sound’s waveform. Fundamental Frequency + harmonics + overtones = timbre Timbre Same Pitch different Timbre + Harmonics Every sound that we hear basically just addition of sound at different frequency Dynamic Range Dynamic range refers to the difference between the quietest and loudest parts of an audio signal, measured in decibels (dB). It represents the range of sound levels that an audio system can capture or reproduce without distortion. Signal to Noise Ratio (SNR) SNR is a ratio that describes the level of the signal of interest (such as music or speech) to the level of background noise in an audio system Signal Noise Clipping Clipping audio is when an audio signal is amplified past the maximum allowed limit, Distortion THD It represents a deviation of the output signal comprised of the fundamental frequency and its harmonic frequencies. The higher the THD level, the more distortion that is in the signal. Example of signals with low and high THD Fast Fourier Transform (FFT) A method to transform an audio signal from Time domain to Frequency domain