by Karen Lederer
[READ THE PHONETICS OF BEATBOXING: APPENDIX 1]
The Acoustic and Auditory Phonetics of Human Beatboxing
Appendix 2 : Presentation of Results: Precisions of measurements, terms and abbreviations used.
Sounds made by the Roland TR 808 Rhythm Composer are referred to in the text as ‘electronic sounds’. ‘Vocally produced’ refers to sounds that are beatboxed.
Where times are indicated there are two values given. The first is the ms form the start of the sound so values across sounds can be compared. The second is the time on the scale shown on the spectrogram. This enables readers to verify the points in discussion.
The EDM is the Energy Density Maximum. Several EDMs may occur in a single sound if there is more than one frequency with high-intensity energy and there is usually one EDM thatis more prominent that the rest. EDMs are different to resonant frequencies because there may only be one resonant frequency in each sound.
Duration of sound is measured from the first indication of sound on the spectrogram to the last indication of sound. Where background noise is present, duration is taken from the first indication of a change in energy levels until the energy returns to the original level of the background noise.
Bursts are measured from the start of the sound until the end of the column of burst energy, i.e. where energy in the burst frequencies is reduced drastically to that of subsequent frequencies. It is usually very obvious where the burst energy ends.
The rate of fade (RF) is calculated in dB/ms. It is measured from the point at which the most intense energy begins to fade until the energy reaches its original level. Where the RF varies throughout the sound, it is split into sections and these are indicated in the table of results. In the beatboxed clave, for example, there are three values for RF. The first is the RF of the burst energy. This is measured from where the highest intensity energy begins to fade until the point at which energy reaches a level consisten with that of the rest of the sound. The second RF value is the rate of fade after the burst i.e. the RF of the rest of the sound. The third value is the average rate of fade of the whole sound. If a sound whose RF varies is compared to a sound with a constant RF, the same value for the sound with a constant RF will be plotted against the varying values of the other sound.
Amplitude rise time is the time elapsed from the start of the sound until its maximum overall amplitude is reached.
Striations are measured in the centre of the column of energy that indicates the striation. Intervals between striations are measured from centre-striation to centre-striation.
Frequency of EDMs/resonant frequencies. Measurements given for EDMs and resonant frequencies are the centre frequencies of the bandwidth the energy occupies. The bandwidths given are ½ bandwidths measured on the spectrum 3dB down from the peak of energy.