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The purpose of this research work is to investigate the relationship between humidity and tone in musical instruments. A basic hypothesis that motivates this work is that normal seasonal variations in relative humidity are thought to alter the tone of instruments constructed from wood. These changes in tone are believed to be due to changes in the dimensions and material properties of an instrument that are a result of wooden components absorbing and adsorbing water in equilibrium with their ambient environmental conditions. To investigate this hypothesis an experiment was conducted with a guitar acclimatized at different relative humidity levels. Sample sounds recorded at each humidity level were then evaluated by the test subjects using a three alternative forced choice listening test paradigm. Subjects were readily able to distinguish sounds recorded at different humidity levels, supporting the claim that changes in ambient humidity can create perceptible differences in instrument tone. A finite difference model was then developed to produce simulated sounds as a function of moisture content (MC being the weight percentage of a piece of wood that is water). The model was validated and further listening tests were conducted to determine the perceptual limit of MC differences. The just-noticeable difference value for MC change was established to be 0.7% MC difference. To be considered imperceptibly stable with respect to tone, materials used to replace traditional soundboard woods would need to have less variability than the equivalent material property changes due to this 0.7% MC difference. Testing of an acetylated plate in terms of its vibration and material properties followed. An increase in both stiffness and density was noted, yet even after modification the vibration properties of the plate were observed to remain within an acceptable range of material properties typical of soundboard grade woods. Instrument builders would likely welcome this new material, as long as its properties can be shown to not vary significantly from traditional choices. A second component of this thesis concerns the application of wavelets in musical analysis. Psychoacoustical signal parameters (PSPs) are a tool used to quantify aspects of sounds, such as brightness or percussiveness. These PSPs are often calculated using the Fast Fourier Transform (FFT), an algorithm that has certain limitations. To address the deficiencies of the FFT a wavelet transform was em- ployed and conventional PSPs were reformulated in the wavelet domain to improve their accuracy. Tonal differences due to changes in MC were shown to be well suited to analysis by wavelet PSPs where improved sensitivity was observed in comparison to the conventional methods. Finally, an acoustical study of the development of the piano from the clavichord to the modern grand piano was conducted. An improved bass response and the presence of more energy in the upper partials, particularly in these bass notes, were concluded to be due to an increase in soundboard area, the introduction of longer string scale lengths, and the use of wound strings for bass notes.

This thesis acts as a first step in connecting the sub jective description of piano tone with quantitative measurements of changes in the vibrational and acoustical properties of a piano. Voicing techniques used by piano technicians are applied to a fully strung test piano and a series of tests are undertaken to measure the effect they have on piano tone. The addition of weights and riblets to a piano soundboard, two commonly practiced methods used to change the tone of a piano and even out the transition between the low tenor and high bass bridges, are examined in detail in this thesis. Modal analysis is the first test method applied and is used to determine the mode shapes and the modal properties of the test soundboard. The addition of small masses and riblets is shown to have the ability to change modal properties to varying degrees and connections are made between the output sound, attachment locations, modification locations, and mode shapes of the soundboard. A new technique, piano tone mapping, is introduced as a visualization method that displays the harmonic structure of the entire piano in one image. Using the technique creates a unique fingerprint of a piano that can be compared in various ways to other pianos. The piano tone maps reveal that initial magnitude and decay rate of the output sound are both decreased for notes with attachment points close to modification locations where weights and riblets are added. Impedance testing is also conducted for a number of different modifications. These tests reveal that riblets and weights each have their own frequency bands of influence, with the weights creating impedance changes primarily below 800 Hz and riblets creating impedance changes above 500 Hz, with a region of overlap between 500 Hz and 800 Hz. Tests also revealed that changes in impedance created by these voicing techniques were local in effect, with a region of influence less than 10 cm in radius extending from the location where the weight or riblet is attached.

This thesis acts as a first step in connecting the sub jective description of piano tone with quantitative measurements of changes in the vibrational and acoustical properties of a piano. Voicing techniques used by piano technicians are applied to a fully strung test piano and a series of tests are undertaken to measure the effect they have on piano tone. The addition of weights and riblets to a piano soundboard, two commonly practiced methods used to change the tone of a piano and even out the transition between the low tenor and high bass bridges, are examined in detail in this thesis. Modal analysis is the first test method applied and is used to determine the mode shapes and the modal properties of the test soundboard. The addition of small masses and riblets is shown to have the ability to change modal properties to varying degrees and connections are made between the output sound, attachment locations, modification locations, and mode shapes of the soundboard. A new technique, piano tone mapping, is introduced as a visualization method that displays the harmonic structure of the entire piano in one image. Using the technique creates a unique fingerprint of a piano that can be compared in various ways to other pianos. The piano tone maps reveal that initial magnitude and decay rate of the output sound are both decreased for notes with attachment points close to modification locations where weights and riblets are added. Impedance testing is also conducted for a number of different modifications. These tests reveal that riblets and weights each have their own frequency bands of influence, with the weights creating impedance changes primarily below 800 Hz and riblets creating impedance changes above 500 Hz, with a region of overlap between 500 Hz and 800 Hz. Tests also revealed that changes in impedance created by these voicing techniques were local in effect, with a region of influence less than 10 cm in radius extending from the location where the weight or riblet is attached.

O presente trabalho tem como objetivo apresentar uma revisão bibliográfica de alguns dos principais conceitos acústicos e psicoacústicos associados à audição humana já desenvolvidos na literatura, de Helmholtz aos dias atuais, com foco no órgão da cóclea, relacionando as áreas de física, neurociências e computação musical, bem como aplicações diretamente derivadas de tal revisão. A partir dos cálculos realizados por Couto (COUTO, 2000) de distribuição da pressão sonora no meato acústico externo, foi calculada a pressão sonora relativa e a impedância acústica ao longo do órgão coclear. Também é apresentado um algoritmo de minimização da dissonância sensorial baseado nos modelos de bandas críticas de Cambridge e de Munique. / The present work presents a literature review on some of the most important acoustical and psychoacoustical concepts associated to human hearing, from Helmholtz to the present day, focusing on the cochlea and connecting concepts of physics, neurosciences and computer music, as well as applications directly derived from such concepts. From the sound pressure distribution model developed by Couto (COUTO, 2000), the relative sound pressure and the acoustic impedance along the cochlea were calculated. An algorithm for minimizing sensory dissonance based on Cambridge and Munich models of critical bandwidths is also presented.

The geometrical characteristics of acoustical radiation are of great importance in instrument design and synthesis, and multiple simplified models have been developed in the past to describe them. In this work two experimental methodologies are proposed and carried out, studying the frequency-dependent radiation in a collection of popular brass instruments with different grades of flaring, and making use of the axis-symmetry of these instruments. The first method uses a scanning linear array and is carefully designed to extract the linear properties of the radiation field. The results of this experimental method are a database of impulse responses distributed in space, and effectively covering a bidimensional on-axis section of the radiation field approximately 0.6 m by 0.9 m. These data can then be used for the validation of a number of simplified physical models used to describe the radiation of these types of instruments. The second method aims at visualising radiation for high amplitude excitation, where shock waves are generated inside the instrument due to non-linear propagation of the plane wave. In this case, the experimental methodology used, taking advantage of the strong density and temperature gradients generated in the air, is an on-axis schlieren optical system. General results of this visualisation show a strong increase in focused directivity at high frequencies and loud playing dynamics, due to the spectral enrichment typical of this family of instruments. The second section of this thesis focuses on the study of playing gestures in the trombone, and could also be applicable to other slide instruments. During glissando playing in the trombone the length of the cylindrical slide section within the bore is altered while waves are propagating. Slide velocities of 2 metres per second are not unusual and result in a (small but measurable) Doppler shift in the wave coming from the mouthpiece before it arrives at the bell. An additional effect is observed in terms of the volume of air within the instrument changing telescopically, leading to a localised change in DC pressure and a resulting flow, which generates infrasound components within the bore. The effects of these playing gestures are investigated in two different setups; one with a high frequency sinusoidal excitation generated by a compression driver, and another one using an artificial mouth to play the instrument. In both experiments the pressures at the mouth or mouthpiece, water key and bell were tracked using microphones and the position of the slide was tracked using a laser distance sensor. Both Doppler shifting and infrasound components were detected for both experimental setups, although the effect on a soft termination such as the artificial lips requires further examination.

Of the many waveforms the bowed string can assume, theso-called "Helmholtz motion" (Helmholtz 1862) gives the fullestsound in terms of power and overtone richness. The developmentof this steady-state oscillation pattern can take manydifferent paths, most of which would include noise caused bystick-slip irregularities of the bow-string contact. Of thefive papers included in the thesis, the first one shows, notsurprisingly, that tone onsets are considered superior when theattack noise has a very limited duration. It was found,however, that in this judgment thecharacterof the noise plays an important part, as thelistener’s tolerance of noise in terms of duration isalmost twice as great for "slipping noise" as for "creaks" or"raucousness" during the tone onsets. The three followingpapers contain analyses focusing on how irregular slip-sticktriggering may be avoided, as is quite often the case inpractical playing by professionals. The fifth paper describesthe triggering mechanism of a peculiar tone production referredto as "Anomalous Low Frequencies" (ALF). If properly skilled, aplayer can achieve pitches below the normal range of theinstrument. This phenomenon is related to triggering wavestaking "an extra turn" on the string before causing thestring’s release from the bow-hair grip. Since transverseand torsional propagation speeds are both involved, twodifferent sets of "sub-ranged" notes can be produced this way.In the four last papers wave patterns are analysed andexplained through the use of computer simulations. Key words: Key words: Bowed string, violin, musicalacoustics, musical transient, anomalous low frequencies,Helmholtz motion

<p>Of the many waveforms the bowed string can assume, theso-called "Helmholtz motion" (Helmholtz 1862) gives the fullestsound in terms of power and overtone richness. The developmentof this steady-state oscillation pattern can take manydifferent paths, most of which would include noise caused bystick-slip irregularities of the bow-string contact. Of thefive papers included in the thesis, the first one shows, notsurprisingly, that tone onsets are considered superior when theattack noise has a very limited duration. It was found,however, that in this judgment the<i>character</i>of the noise plays an important part, as thelistener’s tolerance of noise in terms of duration isalmost twice as great for "slipping noise" as for "creaks" or"raucousness" during the tone onsets. The three followingpapers contain analyses focusing on how irregular slip-sticktriggering may be avoided, as is quite often the case inpractical playing by professionals. The fifth paper describesthe triggering mechanism of a peculiar tone production referredto as "Anomalous Low Frequencies" (ALF). If properly skilled, aplayer can achieve pitches below the normal range of theinstrument. This phenomenon is related to triggering wavestaking "an extra turn" on the string before causing thestring’s release from the bow-hair grip. Since transverseand torsional propagation speeds are both involved, twodifferent sets of "sub-ranged" notes can be produced this way.In the four last papers wave patterns are analysed andexplained through the use of computer simulations.</p><p>Key words:</p><p>Key words:</p><p>Bowed string, violin, musicalacoustics, musical transient, anomalous low frequencies,Helmholtz motion</p>

O presente trabalho tem como objetivo apresentar uma revisão bibliográfica de alguns dos principais conceitos acústicos e psicoacústicos associados à audição humana já desenvolvidos na literatura, de Helmholtz aos dias atuais, com foco no órgão da cóclea, relacionando as áreas de física, neurociências e computação musical, bem como aplicações diretamente derivadas de tal revisão. A partir dos cálculos realizados por Couto (COUTO, 2000) de distribuição da pressão sonora no meato acústico externo, foi calculada a pressão sonora relativa e a impedância acústica ao longo do órgão coclear. Também é apresentado um algoritmo de minimização da dissonância sensorial baseado nos modelos de bandas críticas de Cambridge e de Munique. / The present work presents a literature review on some of the most important acoustical and psychoacoustical concepts associated to human hearing, from Helmholtz to the present day, focusing on the cochlea and connecting concepts of physics, neurosciences and computer music, as well as applications directly derived from such concepts. From the sound pressure distribution model developed by Couto (COUTO, 2000), the relative sound pressure and the acoustic impedance along the cochlea were calculated. An algorithm for minimizing sensory dissonance based on Cambridge and Munich models of critical bandwidths is also presented.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The musician needs to properly perceive the sound in rooms where it operates, either in an environment designed to be performed or to studying and practice music. For this, it is necessary that these sites are acoustically appropriate, enabling the development and enhancement of musical sound perception. In this study six classrooms of the music school of UFSM were characterized by acoustic impulse response measurements and computer simulation, and considered the user s feedback through questionnaires. The questionnaires enabled to understand the preferences of students and music teachers regarding the acoustic quality of a total of twenty rooms for music practice and teaching. Three study rooms and three collective classrooms were the most cited out of those available for the course, which were evaluated by acoustic impulse response, resulting in achieving specified objectives of the main parameters to assess the acoustic quality of rooms by ISO 3382: 2009. The information provided by the musicians proved to be coherent with the measurement data, as the rooms considered dry had presented reverberation times around 0.4 s, and the rooms considered reverberants had reverberation times (RT) around 1.5 s. The six rooms were characterized as clear and well defined rooms, with values for Clarity ranging between 1.0 and 2.0 dB for live rooms and around 22 dB for dry rooms. The definition has remained above 43% for all rooms with Central Time below 50 ms for rooms of greater clarity and less reverberant, and above 90 ms for the live rooms. In general, most rooms were considered weak in relation to acoustic conditioning, and only two out of twenty rooms were considered adequate by most musicians, without receiving considerable negative criticism, being one a study room with a volume of 79.9 m³ and TR equal to 0.4 seconds, and the other a collective classroom with a volume of 327.85 m³ and TR equal to 1.6 s. The computer simulation was efficient for the prediction of the acoustic behavior of the rooms in study and the data obtained in the simulations were compared to the just noticeable difference (JND) for acoustic parameters investigated (T30, EDT, C80, D50 and Ts). A good correlation was observed between measured and simulated data, particularly for parameters related to noise energy in the frequency range from 63 to 8.000 Hz. / O músico necessita perceber adequadamente o som nos recintos onde atua, seja em ambientes destinados à performance, seja em ambientes destinados ao estudo e prática musical. Para que isto seja possível é necessário que estes locais estejam acusticamente adequados, permitindo o desenvolvimento e aprimoramento da percepção sonora musical. No presente trabalho seis salas de aula do curso de graduação em Música da UFSM foram caracterizadas através de medições acústicas da resposta impulso e de simulação computacional, além de considerar a opinião dos usuários mediante questionários. Os questionários aplicados permitiram compreender as preferências dos estudantes e professores de música no que se refere à qualidade acústica de um total de vinte salas para prática e ensino musical. Três salas de estudo e três salas de aula coletiva foram as mais citadas dentre as disponíveis para o curso, as quais foram avaliadas acusticamente através da resposta impulso, resultando na obtenção dos principais parâmetros objetivos especificados para a avaliação da qualidade acústica de salas pela norma ISO 3382: 2009. As informações fornecidas pelos músicos se mostraram coerentes com os dados das medições, de forma que e as salas consideradas secas apresentaram tempos de reverberação (TR) em torno de 0,4 s, e as salas consideradas reverberantes apresentaram tempos de reverberação em torno de 1,5 s. As seis salas se caracterizaram como salas claras e definidas, com valores para Clareza variando entre 1,0 e 2,0 dB para as salas vivas e em torno de 22 dB para as salas secas. A Definição se manteve acima de 43% para todas as salas, com Tempo Central abaixo de 50 ms para salas mais claras e menos reverberantes e acima de 90 ms para as salas mais vivas. Em geral, a maioria das salas apresenta deficiências em relação ao condicionamento acústico, sendo que somente duas das vinte salas foram consideradas adequadas pela maioria dos músicos, sem receber críticas negativas consideráveis, sendo uma sala de estudo com volume de 79,9 m³ e TR igual a 0,4 s, e uma sala de aula coletiva com volume de 327,85 m³ e TR igual a 1,6 s. A simulação computacional se mostrou eficiente para predição do comportamento acústico das salas em questão e os dados obtidos nas simulações foram comparados em relação à diferença no limite do observável (JND) para os parâmetros acústicos investigados (T30, EDT, C80, D50 e Ts). Uma boa correlação foi observada entre dados medidos e simulados, principalmente para os parâmetros relacionados à energia sonora na faixa de frequência de 63 a 8.000 Hz.