## Sound Theory – Sample Rate, A/D Conversion

It has been a long time since I last posted as I’ve been busy with other jobs. I have recently been refreshing my knowledge of sound theory because I know that it will really help my understanding, especially when it comes to mixing. It’s quite easy to learn all the lingo and tech speak when it comes to sound but not actually, really understand how it works. This is my attempt at explaining it briefly in my own terms.

I understand hertz as being one cycle per second and in digital audio this is used to set a sample rate frequency to convert an analogue source to a digital one. This is performed with my sound card which at the moment is an M-Audio FastTrack USB. The FastTrack is a suitably low-mid range unit which has a guitar and mic level input. Since I just need to plug in the USB to the computer its easy to take the inner workings and process of how the sound is delivered to my speakers for granted. In order to record my voice into the computer I would need to convert the analogue signal of my voice into a digital format for the computer to process. This process is Analogue to Digital Conversion or ADC for short. If the ADC uses a sample rate of 50Hz the analogue signal is split 50 times per second and a measurement of the amplitude taken at that moment in time. This measurement is converted to binary, a measurement known as the bit depth. 50 times per second sounds like a lot but CD quality audio is 44,100 times a second! This value was arrived using the Nyquist Theorem which in a principle I will explain in a later post. When exporting audio I normally choose 44.1Khz as a base amount as my hard drive has Terabytes of space and if I need to convert to MP3 the quality is high enough to start with. By understanding the sample rate and its limitations you can choose lower sample rates like 22Khz or 11Khz. For example a telephone conversation has a bandwidth of 3.6 kHz. “Bandwidth is the difference between the highest and lowest frequencies carried in an audio stream” (Source: Audacity Wiki). Telephone speech sits in this frequency range so 8kHz is a suitable sample rate to select and the file size will be smaller which is useful in some cases like web streaming or computer game audio.

So…the higher the sample rate, the more accurately the computer can reproduce the sound. In order for my ears (analogue system) to hear this played back from the computer the digital audio needs to be converted back to analogue. The sound card performs this using a Digital to Analogue Converter (DAC) which directs the speaker cones to move back and forth at the same frequency of the measured waveform causing pressure changes in the air that my ears convert to brain signals. Amazing when you think about it!

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## Pure Data Wind Generator

A few years ago I read a book about synthesis and there was a section about white noise and how it can be used to recreate sounds heard in nature such as the ocean or wind. I wanted to create the sound of arctic wind so I first had a play around with Audacity and then sought to create a patch in an open-source and much loved program called Pure Data. By designing software around my needs I was able to add more features such as automation and filtering.

As in keeping with the pure data community my patch is available here: WindGenerator.pd

## Audio Conceptualising – ‘Dead End’

I have always been very inspired to create sound and music from visual imagery that evokes a sense of exploration and adventure. This generally happens for me if I go for a walk outside in nature like in a forest. I like places that have remnants of objects, machinery and forgotten structures that have in time been engulfed by nature. I have just been experimenting with the idea of audio conceptualising which  involves using still images, pictures and paintings to evoke  these feelings and using sound and music to tell the story of what is being seen.

I found this amazing artwork by Majora28 at DeviantART.

In ‘Dead End’ I used sound design to promote the sense of space and environment as seen in the weather and a feeling of optimism similarly represented from the sun shining through. A plastic bag and a kettle formed the sound of a thunderstorm and I am excited by how realistic it sounds. I am trying to break away from being so literal with my sounds and i’m finally enjoying the challenge of seeing what I can ‘get away’ with.

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## DDL Trunks

This sound was made from a sound recording of a voice that has been time-stretched 800%. The intonation can be heard clearly which gives a distinctive drone sound. I can visualize an air raid siren.

http://soundcloud.com/thinkingsoundblog/fathoms-sample-composition

Abstract

I have drawn my inspirations from a book by Joachim-Ernst Berendt which discusses an Indian musical term named Nada Brahma meaning ‘The Universe is Sound’. The book describes how marine mammals have communicated by using sound waves long before technological advancements were developed. I feel that my piece connects closely with these ideas and I have entertained themes of technology and nature within the piece.

Fathoms is a sonic journey which embodies the notion of communication through the medium of the sea. It unfolds with the sounds of waves lapping on the shoreline of Portsmouth beach and continues on a journey far out into the wide ocean on a boat. The vessel’s sonar rig can be heard bleeping quietly in the background and then gradually increasing in volume as it begins to detect an object in the water. The image on the screen darts around rapidly and it is unclear what lurks below. Suddenly you are plunged deep into the cold, dark water and after a spate of confusion and panic, calm prevails as you are met by a host whales which majestically soar into the depth.

In Depth

Within my piece I have entertained themes of technology and nature using various manipulation techniques. I have recorded the sound of a seagull ‘bird-call’ as it resonates with my inspirations from Berendt’s book that the ocean is filled with sound. He describes that maritime mammals have had the technology to communicate “long before man invented the radio” (Berendt, p. 77). This has inspired me to relate my sample to forms of communication via the animal species, especially in and around the water as this is where seagulls reside.

Marine mammals such as whales and dolphins for example, have the capability to “produce sounds, to transmit and receive and interpret them” and they achieve this with “the aid of echo effects” (p. 77). These ‘echo-effects’ are much like sonar, a communication technology which provides “an underwater acoustic means of determining distance” (UIA, 2005) that maritime mammals have implemented to “locate partners, targets, objects and enemies as well as fathom the depth of the water” (Berendt, p. 77). I think that sonar is like a technological copy of marine species’ communication methods. I have put this process into practice by collecting a natural sound from its environment, i.e. a seagull, and manipulating and reproducing it using technology. I have used an audio editor and computer sequencer, Audacity and Cubase respectively, to facilitate my ideas for the piece. A seagull’s call usually begins with a tone that slowly rises in pitch and suddenly jolts in to a series of loud repetitions of identical tones. With the intention of capturing the most variation, I cut my 1 second sample from a section which contained both the rising tone and part of the repetition.

Pierre Schaeffer was a French enthusiastic experimenter who pioneered electro-acoustic sound manipulation techniques. He was a “technician with Radiodiffusion Française” in 1936, (Dhomont, 2007) who “invented musique concrète”in 1948 (Smalley, 2007)and later went on to establish Studio d’Essai from which he produced many pieces of work (Dhomont, 2007). Pierre began his experimentations with (78 r.p.m.) record technology until “the introduction of tape machines in 1951” (Emmerson, Smalley, 2007).

Musique concrète “originally conveyed the idea that the composer was working directly (concretely) with the sound material”. This opposed the alternative method whereby composers used a “symbolic system of notation” to represent “sounds to be made concrete by instruments and/or voices”. The latter method was named ‘Musique Abstraite’ by Pierre Schaeffer which literally means abstract music (Emmerson, Smalley, 2007). Pierre stressed that musique concrète was as a process which did “not, as is frequently thought, refer to the musical use of noises” but instead with the organisation of sounds. He believed that all recorded sounds such “music, noises, animal cries” should be regarded as ‘sound objects’ as they are all “experienced in the same manner” (Dhomont, 2007).

Pierre discovered that in order to “remove major problems of association” i.e. timbre (Manning, p. 31), it was vital to “remove the sound from its context in order to eliminate “any sources retaining a significant proportion of their identifying characteristics” (p. 34). I employed this technique so that I could assign certain ideas with the sample in a compositional method. I altered and manipulated my sound object to remove its identifying characteristic’s especially with one technique of time-stretching the audio (altering the tempo but not the pitch). This is exactly what Schaeffer had done by “investigating the effects of playing recordings at different speeds” in his studio (p. 32). However, at the start of the piece where I clearly wanted to represent the sounds perceived at a beach, I deliberately used the sample without alteration. What fascinated me was that I was able to create harmonies and tones, some of which sounded very similar to real instruments.

Pierre created a piece called “Suite pour quatorze instruments”, (p. 33), which contained five different movements. One of which, called ‘The Gavotte’, used “interpretations of one short musical phrase on different instruments, juxtaposed to create a set of variations”, (p. 33). I have developed a library of sounds in this manner but instead of using instruments to create variations, I have worked ‘concretely’ with the sound by using numerous processing effects on the sample. Schaeffer found that the Gavotte proved unsuccessful because “despite many interpretations and transpositions it retained many of its original characteristics (p. 33), Pierre was limited to analogue tape techniques such as speed changing, repetition, mixing and cutting with his tape machines (Emmerson, Smalley, 2007) whereas I had access to significantly advanced technology and a vast number of processing effects at my disposal so that I could overcome this problem.

In 1974 François Bayle suggested the idea of ‘Acousmatic music’ (Dhomont, 2007) which “ruptures traditional notions of music reception” by removing the listener from “seeing the sources or causes of the sounds” (Emmerson, Smalley, 2007). Acousmatic, referred to akusmatikoi, whereby pupils ofPythagoraswere “required to sit in absolute silence while they listened to their master speak” from “behind a screen”. Schaeffer created a piece called ‘Traité des objets musicaux’ in (1966) which “compared the role of the tape recorder to the screen of Pythagoras” in order to emphasise the “concentrated listening facility” thus encouraging “a better appreciation of the detailed abstract attributes of sounds” (Emmerson, Smalley, 2007). Bayle “developed the concept of ‘images of sound’” which he suggested would “give rise to three kinds of mental images: iconic, diagrammatic and metaphorical” (Dhomont, 2007). By isolating a sound from its environment and transforming it, I was able to create acousmatic music.

I have aimed to convey emotions, locations and imagery with themes of travel, communication, industrial sounds, the ocean, technology and natural creatures using musique concrète techniques. I set out to achieve calm and serene atmospheric music which reflected the calmness of the ocean and I did this by using delays, noise filters to mimic lapping waves on the beach and chorus effects which produces a warm sound.

I have designed my piece to be a collection of mental ideas attached to the sound. To recreate sounds that one may associate with sea creatures, I transposed the whole sample a few octaves which created a peculiar and mysterious sound. Because the sound was a lot deeper than normal, the recognisable attributes had been removed. Also, to further Berendt’s writings about ‘the aid of echo effects’ I have used lots of delay effects within the piece which creates the illusion of space. The “intelligent use of dynamics” creates “an illusion” of perspective (Schafer, p. 34) which I have achieved by automating volume control and pan settings. Pierre Schaeffer recognised this technique and in 1951 he used “four channels to create a play of perspectives and trajectories at the Théâtre de l’Empire in Paris” (Emmerson, Smalley, 2007).

To represent sonar like the type, for example, that is generally associated with submarines from war films; I have cut a small section from the end of the sample and applied a reverb insert with a long decay and a slow attack. I have represented technology as if a computer operating produced a sound. A computer’s fundamental operation relies on processing random strings of binary digits (zero’s and ones) and to mimic this randomness with the sample I have applied time stretching devices and a ‘bitcrusher’ insert. This works by varying the bit depth and sample rate from the frequency bands of the incoming signal and I downsized the sample rate to create a ‘crushed’ version of the sample. I represented electricity by using delays, and bitcrusher’s to imitate pulses of current flowing down wires.

In conclusion I have discovered that musique concrète and electro acoustic processes are an important technique for musicians to experiment with in order to develop originality and avoid clichéd compositions. Schaeffer often encountered issues in which he found that his alterations were constrained to his habits and structures which had “conditioned the way in which he carried out his processes of analysis and re-synthesis” (Manning, p. 34).

By creating a sample library of manipulated sound objects from a single second’s worth of sound, I have discovered that there are endless possibilities for sound design. I was able to represent the sound of ‘boats’, a ‘mechanical’ noise or something similar to a violin being played, for example. This has nurtured my ability to be more creative and less dependant on pre-made sounds and instrument presets that are included with sequencing software. I have enjoyed the challenge of ‘working’ to attain the sound that I was trying to represent by discovering the method first hand.

Bibliography

Berendt, Joachim-Ernst. (1983). The World is Sound. Nada Brahma. Toronto: Destiny Books

R. M, Schafer. (1967). Ear Cleaning. Toronto: Berandol Music Limited

Manning, P. (2004). Electronic and Computer Music. [Electronic Version]. p. 31 of 1-497

F. Dhomont:‘Schaeffer, Pierre’, Grove Music Online ed. L. Macy (Accessed 9 May 2007), http://www.grovemusic.com/shared/views/article.html?from=search&session_search_id=213300856&hitnum=1&section=music.24734

D. Smalley: ‘Groupe de Recherches Musicales’, Grove Music Online ed. L. Macy (Accessed 13 May 2007), http://www.grovemusic.com/shared/views/article.html?from=search&session_search_id=685116323&hitnum=12&section=music.42131

S. Emmerson, D. Smalley:‘Electro-Acoustic Music’, Grove Music Online ed. L. Macy (Accessed 9 May 2007), http://www.grovemusic.com/shared/views/article.html?section=music.08695

F. Dhomont: ‘Bayle, François’, Grove Music Online ed. L. Macy (Accessed 13 May 2007), http://www.grovemusic.com/shared/views/article.html?from=search&session_search_id=1158329428&hitnum=1&section=music.02386
Ultrasonic Industry Association (U.I.A). (2005). Retrieved May 6, 2007, from, http://home.att.net/~Berliner-Ultrasonics/us-gloss.html

## what does sound recording mean to me?

In my experience field sound recording is capturing an indoor or outdoor environment with at least one microphone and focusing on either a mass bed of sound (ambience) or ‘zooming-in’ on individual events (I like to call these sound spots). The purpose is to accurately capture the sound for future re-production, re-arrangement and playback. I had often thought that sound recording – in the field recording sense – that is, outside of the studio, could be compared with photography. However, the more I think about it, a photographer constructs an image based on a number of factors which include lighting, framing, camera placement, image composition and more. It is also subject to personal choices, ideas and methods. In this sense each photographer can apply their own unique stamp on a photograph.

I now think that a photographer is more like a sound designer because by using a range of tools (methods to construct the image) the final outcome is a result of such layering, artistic choice.

I think that field sound recording is more scientific than creative. It is in its very nature methodical. Surveying which is “the science of accurately determining the terrestrial or three-dimensional position of points and the distances and angles between them” (Source:  Wikipedia (Surveying)) has a similar method to sound recording. Is this method the same as field sound recording except with the use of different equipment ‘recording’ equipment?

I intend to find answers to the following questions

• Is field sound recording a sustainable vocation?

There are already thousands of recorded sounds available to purchase either separately or in packs that can also be freely distributed, e.g under Creative Commons licences. How does a sound recordist justify doing this again. I think some of the following reasons apply:

1. They couldn’t find the sound that they were after.
2. They wanted to record the sound rather than paying for it.
3. It will form part of a sound pack that they could monetize.
4. The quality of the recorder wasn’t the right fidelity.

This leads into my next question:

• What happens when all the sounds in the world are recorded? Why do field sound recordists continue to record what has already been recorded?
• What are the personal aims of sound recordists ? Is it for financial gain (e.g. creating a sample library) ? Or is it for the experience, experimentation etc.? (*examples*..)

Collecting

I watched a video from Sonic Terrain called Alan Burbridge – The Sound Collector. The way that he describes what he does is very interesting to me. I’ve roughly transcribed what he said.

“I don’t think it’s the technology, I think it’s the birds to some extent but I think it’s more of a sanitised hunter-gathering……People collect match boxes, or they collect train numbers, or airplane numbers or they tick off how many formula one races they’ve been to. For me, I’m, as I say a sanitised hunter gathering so I’m going out there I’m hunting my birds, I’m getting close enough to them to get a good recording and then I’m leaving them alone, not causing them any harm. So it’s a bit like going out and taking nothing but photographs and leaving nothing but footprints. It’s the same sort of thing.”

Matthew Herbert

“I used to be a collector, I used to always have something in my pocket. Oh, a funny motorbike! Oh, a strange bird! But now I’m not so interested in that. For me that’s like being a photographer and just taking pictures of anything…There has to be a reason why you are recording something otherwise its just like you’re a consumer. Say, Okay I have cheese one day and ham the next.”

• There is a need for a surveyor to re-record data in the future of a previously mapped site because maybe the land has changed or boundaries have been altered – does the same apply to sound recording? – We know that the soundscapes change across time but is this so evident in natural places that appear unchanged over a long period of time (e.g. not affected by human progression).
• Is there an element of keeping up to date with the latest technology of recordings? As the bit rates and sample rates increase does this influence a re-recording?
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## Welcome

Hello and welcome to thinking sound. This is my first ever blog and I have created it to write down my thoughts on what I like about sound. I could describe myself as a sound designer, field recordist and musician but it is not my profession. I am just developing my hobby and answering questions along the way. I have used WordPress in the past to create websites and decided it would be the best tool to start blogging for the first time. I am looking forward to developing my creative writing skills and sharing ideas and experiences with fellow bloggers.