Phase 1 Exam

Question 1

Harmonic Motion

Answer 1

A tone causes air molecules to oscillate in a regular pattern causing the air pressure around the molecules to rise and fall.

Question 2

Compression

Answer 2

When air molecules are pushed together as a result of sound waves moving against them (rising air pressure)

Question 3

Rarefaction or Decompression

Answer 3

As sound waves travel, the air molecules are pushed further apart and have more room to travel (falling air pressure)

Question 4

Definition of Periodic

Answer 4

Something that changes over time in a regular pattern is defined as “Periodic”

Question 5

Sound Propagation

Answer 5

The manner in which sound travels by causing a disturbance in the air pressure of the air molecules. It can travel through air, water, and solid matter.

Question 6

The speed of sound through the medium of air during normal temperature and barometric pressure conditions is:

Answer 6

1100 feet per second or 335 meters per second. (The higher the temperature, the faster sound travels.)

Question 7

The physical manifestation of sound is created when:

Answer 7

A wave of rising and falling air pressure is transmitted to the listener’s ear.

Question 8

Define frequency and the term hertz and how it applies to sound waves:

Answer 8

The Frequency of a wave is the number of cycles per unit time, usually measured in cycles per second. Hertz is the term used to define frequency as cycles per second and is abbreviated as Hz.

Question 9

What is the definition of “cycle” as it pertains to sine waves and types of sound waveforms?

Answer 9

A cycle of a sine wave is a section of an existing wave from a starting position to the first moment it returns to the same position after completely going through compression and rarefaction.

Question 10

What is the difference between the wavelength of a sine wave and the period of a sine wave?

Answer 10

Wavelength defines the distance that the wave travels (propagates) and the period defines the time it takes for the sine wave to travel.

Question 11

What is the formula for calculating the wavelength of a sound wave?

Answer 11

λ=v/f where λ (lambda) is wavelength, v is velocity, and f is frequency. So, the wavelength of a sine wave at 100hz in feet per second is 1100/100= 11 feet.

Question 12

What is the formula to calculate the frequency of a sine wave?

Answer 12

number of cycles divided by time
(so if there are 3 cycles in a sine wave within a .001 period of time, the frequency is 3000hz)

Question 13

The dominant frequency of a tone that gives the note its pitch is called:

Answer 13

The fundamental frequency.
(To calculate a frequency that is an octave above the fundamental, you multiply by 2. A440 an octave above is A880. An octave above that? A1760.)

Question 14

The ADSR initials of the envelope stand for:

Answer 14

Attack, Decay, Sustain, Release

Question 15

Briefly describe the phenomenon of comb filtering:

Answer 15

When a complex wave is mixed with a delayed copy of itself, thus causing some frequencies to cancel, and others to reinforce.

Question 16

To achieve 100% phase cancellation of two sine waves with identical frequencies, periods, and wavelengths, you must delay the 2nd sine wave by:

Answer 16

180 degrees

Question 17

The decibel is defined as:

Answer 17

A numeric value that measures levels of sound intensity, or the magnitude of fluctuations in air pressure caused by sound waves.

Question 18

dBSPL stands for:

Answer 18

Decibel Sound Pressure Level.

Question 19

What is the main reason the decibel is used instead of the Pascal to measure sound loudness levels?

Answer 19

The decibel is logarithmic in nature, which is represented by fewer numbers between sound level values, thus making it easier to interpret the difference in levels.

Question 20

The low level threshold of human hearing is?

Answer 20

The threshold of perception, or 0 dBSPL.

Question 21

The high level of threshold of human hearing is?

Answer 21

The loudness level of a sound where the human ear begins to feel pain and will most likely cause permanent hearing damage to the listener. This level is between 120 and 130 dBSPL.

Question 22

These are the different levels of voltage for recording equipment:

Answer 22

Microphone level: -30 dBu
Instrument level: -20 dBu
Consumer line level: -10 dBu
Guitar amplifiers: 0 dBv
Professional line level: +4 dBu

Question 23

Define “Sampling” as it pertains to Digital Audio technology:

Answer 23

The process where the air pressure amplitude of a sound wave is measured at equally spaced moments in time. Once sampled, the sound wave amplitude and frequencies get recorded as binary numbers.

Question 24

Sampling rate frequency definition for Digital audio applications:

Answer 24

Sampling rate denotes the number of “samples” or snapshots that are taken of an analog audio signal within a certain period of time. 44.1k sampling is 44,100 samples per second.

Question 25

Quantization error definition for Digital Audio applications:

Answer 25

Quantization error is the difference between the actual value of the analog waveform and the closest digital value which can introduce digital noise depending on the bit depth.

Question 26

Signal to noise ratio formula:

Answer 26

6xn=S/N Where “n” is the bit depth. So 6x16=96. The signal to noise ratio at 16 bits is 96db (headroom / dynamic range).

Question 27

Nyquist theorem definition:

Answer 27

In order for an analog signal to be accurately sampled, the sampling frequency must be 2 times the frequency of the highest analog frequency component. If the nyquist theorem is not followed, then “Aliasing” can occur, which will create an inaccurate representation of the original sampled sound (poor sound quality, digital distortion).

Question 28

What is the difference between sampling rate and bit depth?

Answer 28

Sampling rate describes how many samples are taken per second during analog to digital conversion. Bit depth pertains to how many digital bits or binary numbers can be used to represent the amplitude values of the sound wave. Higher bit depth enables the sample to have a higher level of accuracy and a greater signal to noise ratio, because of the higher possibility of digital number representations.

Question 29

What is the signal to noise ratio (S/N) of an Analog to Digital converter at a bit depth of 16?

Answer 29

S/N (signal to noise ratio) is calculated as 6xn= S/N where n is the bit depth and the S/N value in this case is 96. 6x16=96. The higher the S/N, the better the quality of the recording.

Question 30

What does 0 dBFS stand for?

Answer 30

0 decibels relative to full scale.