Blog Five: Final Blog

This module has been truly fantastic! I have learnt things that I will keep with me for my whole career. There has also been a lot of learning curves, which in hindsight is quite useful as I know what works well, what doesn’t, and in turn, if I was to do this module again, what I would do differently.

For the project, in my group was (Richard) Louis Hughes, Sophie Hughes, and myself Joseph Kearney. When it came to actually deciding on a specific topic for our project, it was a very hard to choose. We all had different ideas, and different views on what we wanted out of the project, so it was difficult.

After going back and forth on a few different ideas, Sophie seen something about a Tattoo Convention that was coming to Glyndwr University. She thought that this convention would be the perfect scenario for our project. We all agreed, and started to plan and contact the event organisers. Thankfully, the event organisers got in touch with us, and gave us the green light for our project. Sadly, this was the only contact we received from the organisers, so therefore our plan did not come to light.

We then were back to square one.

We got together and discussed different ideas that we had, but again we were hitting a dead end. We left the discussion with no new ideas so we were at a crossroad. Then, Sophie and Louis, asked me what I thought about interviewing a band that were visiting the area. Immediately I agreed to this as I knew that it was an amazing idea. I then researched the band that we were interviewing, and I did not realise how important this band were. The band is Calfari, they are a welsh speaking band, and all of their songs are written and sang in Welsh. For me, an Englishmen, I was actually amazed. Listening to the band perform and the passion that they put into their lyrics is truly mesmerising. What is even more interesting is, that I can not understand their language, however their songs still captivate me, and make me want to listen.

We also interviewed a student, Stuart, who is currently studying Sound at Glyndwr University. This was interesting, too. As we really got to understand Stuarts passion, and why he has such passion.

We also had other interviews planned, however the fell through. Although, I thought that content we already had, covered our chosen project.

If I was to do this project again, I would definitely try harder to get a plan together, and possibly a Plan B, so if our first plan doesn’t go as planned we would have something to fall back on, as this would in turn save time and give us that extra time to focus on editing.

I would also, try and choose a plan that did not rely on other people as much as our first plan did, as this caused so much trouble, which is why our first project never got off the ground.

In summary, it was a really good project, which I have learnt from and thoroughly enjoyed!

(Richard) Louis Hughes, left. Joseph Kearney, right.

Blog 4: Parameters of digital compressors and gates & Loudness measurements – (LUFS and True Peak)

The main aim of a compressor is the limit the level of the loudest signals. The mail reasons for compressing these signals are:

1. Controlling the energy of a signal
2. Controlling the peak levels of a signal
3. Reduce the dynamic range on a signal.

Threshold

When this level has exceeded, the processor starts compressing.

Attack Time

This is the amount of time it takes for the signal to fully compress after surpassing the threshold level. Minimum attack times may oscillate between 50 and 500 microseconds. This purely depends on the type and brand of unit, while maximum times are in the ranges of 20 to 100 microseconds. These ranges however, sometimes are available as slopes in dB (decibel) per second.

Fast times may even create slight distortion, since they change the waveform of low frequencies, which are slower.

Knee

Some compressors have the option of Knee. It is a control that allows the selection of transition between the processed states and the unprocessed states. Usually, you would get the option of a soft knee or a hard knee. The control may also allow the selection of the two types of knee. Soft knee compression is known as OverEasy, as used by some branded compressors. The soft nee allows for a smoother and therefore more gradual compression.

 

LUFS

LUFS stands for Loudness Units Full Scale. When measuring loudness, there are three different terms that are essential. LKFS (Loudness K-weighted Full Scale), LUFS (Loudness Units Full Scale), and LU (Loudness Units). The fact these terms are very similar, and describe the same thing causes massive confusing across the whole industry.

True Peak

Since loudness measuring is based on an algorithm that builds on a study of subjective perception, in theory; program material that complies with the determined LRA and programme loudness of a certain broadcast standard can actually overload if done the traditional way. Therefore, the normal way is also the part of many broadcast standards. Broadcasters M U S T use a true peak metre.

Blog 3: Parameters of Delay & Reverb Units

Inverse Square Law

The inverse-square law is a principle that expresses the way radiant energy propagates through space. The rule states that the power intensity per unit area from a point source, if the rays strike the surface at a right angle, varies inversely according to the square of the distance from the source.

The law says that in a free space the intensity of a sound drops by approximately 6dB for each doubling distance from the source. As working in a free space is quite impossible, we still use this figure as it is workable. This means that each time, you double the distance between the sound source and a microphone, but the power of the sound drops by 75%, which is a significant loss of level, this equates to 6dB.

Critical Distance

Critical distance is that physical place in your room where the room sound from your room is mixed with the direct sound from the speakers. The direct sound is that sound which travels in the shortest distance between two points which is a straight line.

Reflections from the surfaces of the room, intermix with the sound from the sound outsource (Speakers) at a balance point, where reflections and direct sound have an equal sound energy. This is the Critical Distance point in your room.

Finding this spot can be quite difficult. If you are in a rectangular room, it will be somewhere along the middle of the room. You will know when you find it, as you can hear the direct sound, as well as, the sound of the room.

 

Early Reflections

Reflections can be divided into two groups: early reflected sounds and late reflected sounds.

The early reflected sound leaves the loudspeaker and then bounces off one of the boundaries of the room* before reaching the ears of the listener.

* these are: ceiling, floor, front wall behind speakers, rear wall behind listeners, left side wall, right side wall.

Early reflections are really important compared to late reflected sounds. This is seen by looking at a typical frequency response at the listening position and comparing it to the measurements of the speaker.

Early reflections tell you something about the position and distance of the sound source, they also can tell you something about the general geometry of the room, too. The later reverb signal tells you more though, the overall size and reflectivity of the space, however there is nothing directional left in the signal. Early reflections in a reverb do the same thing, but they also do more.

Blog 2: Gain-staging

This specific blog, was very difficult for me to write. As I missed this lecture due to unforeseen circumstances. Therefore, each topic I have discussed, I researched.

Unbalanced Interconnections

Unbalanced signal lines are characterised by the fact that the cable and connectors use only two conductors, a centre conductor surrounded by a shield.

Examples of unbalanced wiring are found in tip/ sleeve (TS) 6.25mm (1/4”) guitar cords and the cables used with many CD players and tape decks which terminate with RCA phono type connectors.

An unbalanced cable consists of two connectors with two conductors each, connected by two wires inside the cable—a signal wire and a ground wire.  You can quickly (in most cases) identify a cable designed to carry an unbalanced signal by its connectors: because each wire has to terminate at the connector with its own contact point, an unbalanced cable requires only two conductors at the connector.

Balanced Interconnections  

A balanced connection cable consists of a pair of inner conductors enclosed by a screening braid

 A balanced cable, by contrast, has three conductors in the connector and three wires in the cable: two signals wires plus a separate ground wire. As in the unbalanced cable, the ground wire still surrounds the signal wires and is used as a shield against interference. But what makes a balanced cable special is the way the gear utilizes that extra signal wire.

Common-mode Rejection

Common-mode rejection is the ability of the differential amplifier (which sits between the oscilloscope and probes as a signal-conditioning preamp) to eliminate the common-mode voltage from the output. Now, the ideal differential amplifier would remove all of the common-mode signal, or the voltage common to both sides of the differential pair.

Common-mode voltages can come from numerous sources, including an ambient radiated signal coupled into both lines, an offset from signal common created by the driver circuit, or a ground differential between the two ends of the differential circuit. Regardless of its cause, it’s not the common-mode voltage that’s of interest, but rather the differential voltage. Thus, the measure of how good the differential amplifier is at getting rid of common-mode voltage is its common-mode rejection ratio, or CMRR.

Be mindful that the CMRR of an amplifier changes with frequency. High-performing differential amplifiers start at very high CMRR ratings of as much as 100,000:1 and can maintain high CMRR values over a wide bandwidth. Meanwhile, high-voltage differential probes will provide good CMRR at dc. But as signal frequencies rise, CMRR deteriorates.

Reverberation Time RT60

The RT60 reverberation time measurement is defined in the ISO 3382-1 standard for performance spaces, and the ISO 3382-2 standard for ordinary rooms.

RT60 is measured in seconds and often stated as a single value. The actual measurements span the frequency band from 50 Hz to 8 kHz with 1/1 or 1/3rd octave resolution. Rooms have individual absorption capabilities for each frequency, so the RT60 values within each band will vary.

Microphone Types

I used the following site to research the different types of Microphones that are used today.

https://www.dawsons.co.uk/blog/the-different-types-of-microphones-explained

Polar Patterns

The polar pattern of a microphone is the sensitivity to sound relative to the direction or angle from which the sound arrives, or easier worded how well the microphone “hears“ sound from different directions. The most common types of directionality are: Omnidirectional, Cardioid and Supercardioid.

 

 

Blog 1: Fundamentals of Sound

In this lecture, we covered the basics of Sound, and what Sound is; therefore introducing us to the World of Digital Audio.

Frequency

Frequency is basically set by counting the number of cycles per second, and is measured in hertz (Hz).

One Cycle = 1Hz

The human ear, can detect sound from 20Hz to 20,000Hz (20kHz).

Animals have a much different hearing capability than humans do. The below chart was taken from Survival Life, which has an interesting article on how sound frequency causes pain. 

Wavelength

Where frequency measures the number of cycles per second, A Wavelength is the measurement of a complete cycle, therefore is inversely proportionate to frequency. The recognisable symbol for Wavelength is λ.

Below is a diagram from BBC Bitesize. The site is primarily for High School students, but nevertheless has fantastic information on wavelength that in turn is massively relevant for this module. A quote from their site follows which helped me understand Wavelength a little more:

The wavelength of a wave is the distance between a point on one wave and the same point on the next wave. It is often easiest to measure this from the crest of one wave to the crest of the next wave, but it doesn’t matter where as long as it is the same point in each wave. 

Amplitude

An Amplitude describes the amount of energy present in a Signal. As seen in the diagram under Wavelength, where the wavelength measures the length of the wave, the amplitude measures the height. The greater the amplitude, the louder the signal will be as it will put more pressure against the human ear. How loud a signal sounds, is measured in decibels (dB).

Amplitude is related to, but not the same as Volume.

Decibels (dB)

The decibel is based on the logarithm of the ratio between two numbers. It also describes how much larger or smaller one value is than the other. If the reference value is fixed then it can be used as an absolute unit.

dB = 10log10(P1/P2)

The decibel is strictly 10X the logarithm to the base ten of the ratio between the powers of two signals.

10log(2/1) = 3dB

The difference in dB between a signal with a power of 1 watt and one of 2 watts is.

If the dB is used to compare values other than signal powers, the relationship to signal power must be taken into account.

• Voltage has a square relationship to power.
• Ohms Law W=V2/R.
• therefore to compare 2 voltages:

1.    dB = 10log(V12/V22)
2.    dB = 10log(V1/V2)2

The difference in dB between a signal with a voltage of 1 volt and one with 2 volts is.

20log(2/1) = 6dB

So a doubling in voltage gives rise to an increase of 6dB, and a doubling in power gives rise to an increase of 3dB.

A similar relationship exists to acoustical sound pressure and sound power.

Phase

complex wave = When multiple sound waves are combined they create a single wave.

destructive interference = Can be a result of two waves of equal amplitude and frequency but differing states of compression or rarefaction.

Phase becomes an issue when more than one channel is used to record a single source, such as stereo micing a guitar, multi-micing a drumset, or using a microphone/DI combo for bass. Recording “mono overdub style” avoids these issues, but doesn’t give you a dynamic stereo field. In fact, the problem most often manifests itself in when converting tracks from stereo to mono.

First blog post

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