1. What is a sound from a physical point of view?
   A sound is the result of a mechanical disturbance of some object in a physical medium, such as air.
2. How does a computer represent a sound in its memory?
   The computer represents sounds as binary numbers.
3. What are ADC and DAC converters?
   An ADC is a device that converts a waveform into a succession of binary numbers, each representing the voltage level at a given instant. A DAC is a device that converts binary numbers (i.e., digital sound representation) into analog signals, or electrical voltage.
4. What do you understand by digital sound sampling?
   Digital sound sampling is the conversion of a sound from an analog representation to a digital representation.
5. What is the sampling rate most commonly used in computer sound design systems?
   The sampling rate frequently used in computer sound design systems is 44100 Hz, that is 44100 measurements per second.
6. What is aliasing distortion and what should be done to avoid it?
   Aliasing distortion happens when the sound that is being sampled contains partials that are higher than the Nyquist frequency. The Nyquist frequency is calculated ass half of the value of the sampling rate. Aliasing distortion can be avoided by using high sampling rates.
7. What sort of information is provided in a sound file besides the raw sound samples?
   Usually there is an initial portion, called the head of the file, which contain information such as the sampling rate used, the size of the word and whether the sound is mono or stereo.
8. What is MP3?
   MP3 is a popular method for optimising the representation of samples in order to reduce the size of the sound file. MP3 works by eliminating sound components not normally audible to humans.

 

1. What does the acronym MIDI means?
   MIDI means Musical Instrument Digital Interface.
2. What is MIDI for?
   MIDI is a protocol to communicate with synthesisers and samplers, designed for recording and playing back digital music.
3. What are MIDI channels?
   MIDI channels are like an electronic address that labels a packet of digital information, specifying its ultimate destination. They are not separate physical connections. Each MIDI channel corresponds to a distinct stream of data and could be related to a different timbre (or instrument).
4. What are MIDI modes?
   MIDI modes are devoted to governing how each piece of equipment handles the MIDI channels. There are 4 standard MIDI operating modes: “Omni on/poly”, “Omni on/mono”, “Omni off/poly” and “Omni off/mono”.
5. What do you understand by "General MIDI"? Why it is important?
   General MIDI, referred to as GM or General MIDI System level 1, is a standard system for MIDI files. It is a standard instrument assignment for the 128 available program numbers. It is important because all manufacturers of MIDI equipment agreed to adopt GM in their equipments.
6. What are the advantages and disadvantages of MIDI sequencers in relation to a multi-track audio recorder.
   A sequencer is a program in a computer or stand-alone keyboard synthesiser that puts together a sound sequence from a series (or sequence) of MIDI events. The advantage of a MIDI sequencer is that allows the user to record and edit a musical performance without using an audio-based input source; it works as a virtual multi-track recorder for MIDI information. This saves storage space and does not require much computer power. On the other hand, MIDI sequences cannot capture audio signal; the quality of the playback depends on the quality of the MIDI synthesiser used.

 

 

1. What is the fundamental idea behind the additive synthesis technique?
   The fundamental idea behind additives synthesis is that complex tones can be created by the summation, or addition, of simpler ones.
2. Which acoustic musical instrument best resembles the functioning of an additive synthesiser?
   Pipe organs or Hammond organs resembles the way in which additive synthesis works.
3. What is FFT?
   FFT stands for Fast Fourier Transform. It is a technique to analyse the spectrum of a sound.
4. Why is FFT important for additive synthesis?
   FFT is important for additive synthesis because it helps us to estimate the values for the oscillators that produce the partials of the synthesised sounds.

 

1. How does simple FM works?
   The basic FM technique works by modulating the frequency of a carrier oscillator by the signal of a modulator oscillator.
2. What is the FM term for the amplitude of the modulator oscillator?
   In FM, the amplitude of the modulator oscillator is called frequency deviation.
3. How the sidebands of simple FM are calculated?
   The spectrum of an FM sound is composed of the offset carrier frequency (ƒ_c) and a number of partials on either side of it, spaced at a distance equal to the modulator frequency (ƒ_m). The partials generated on each side of the carrier frequency are usually called sidebands. The sideband pairs are calculated as follows: ƒ_c + k × ƒ_m and ƒ_c - k × ƒ_m where k is an integer, greater than zero, which corresponds to the order of the partial counting from ƒ_c.
4. What happens with the energy of the offset carrier frequency as the modulation index increases?
   Increasing the modulation index produces sidebands at the expense of the power of the carrier frequency. The greater the value of the modulation index, the greater the number of generated partials and, therefore, the wider the distribution of the power between the sidebands.
5. What is the FM parameter that if often used to control the spectral evolution of the sound?
   The modulation index controls the spectral evolution of the sound. The modulation index is the ratio between the frequency deviation and the modulator frequency.
6. What type of frequency ratio produces metallic bell sounds?
   Metallic bell sounds are produced when ƒ_c is equal to any integer and ƒ_m is not equal to an integer; for example 2:1.31.
7. What type of frequency ratio produces square-like waves?
   Square waves are produced when ƒ_c is equal to any integer and ƒ_m is equal to any even number; for example, 2:1.