The double bass and cello sections in the orchestra transmit vibrations to the stage floor through the end pins. Whether or not these vibrations may contribute to the perceived sound in the hall has been investigated since the 1930s. In this study the conditions for an efficient transfer of instrument vibrations to the floor, as well as the radiation from the floor to the audience area, are investigated. The study includes measurements of the impedance matching between bass and stage floor, the vibration velocity transfer to the floor via the endpin, and radiation from point-driven bending waves in the stage floor well below the coincidence frequency. The impedance conditions and radiation properties of the stage floors of five concert halls were investigated. In the two most promising halls, full-scale experiments were run with an artificially excited double bass supported via the end pin on the stage floor and on a concrete support below, respectively. The contribution from the stage floor radiation to the sound level in the audience area was 5 dB or more between 30 and 60 Hz. This range covers the fundamental frequencies over one octave starting from the lowest note (B0) of a five-string bass.

This study investigates the acoustical and perceptual influence of the string parts outside the speaking length in grand pianos (front and rear duplex strings). Acoustical measurements on a grand piano in concert condition were conducted, measuring the fundamental frequencies of all main and duplex strings in the four octaves D4-C8. Considerable deviations from the nominal harmonic relations between the rear duplex and main string frequencies, as described by the manufacturer in a patent, were observed. Generally the rear duplex strings were tuned higher than the nominal harmonic relations with average and median deviations approaching _50 cent. Single keys reached +190 and -100 cent. The spread in deviation from harmonic relations within trichords was also substantial with average and median values around 25 cent, occasionally reaching 60 cent. Contributions from both front and rear duplex strings were observed in the bridge motion and sound. The audibility of the duplex strings was studied in an ABX listening test. Complete dampening of the front duplex was clearly perceptible both for an experiment group consisting of musicians and a control group with naive subjects. The contribution from the rear duplex could also be perceived, but less pronounced.

The question whether or not double basses can benefit from a compliant and radiating stage floor in the low end of their tonal register, similar to the well-known tuning fork–tabletop effect, was examined through field experiments in five concert halls. The topic comprises several aspects: (1) How well the mechanical impedances of double basses and the stage floor match, (2) amount of vibration velocity transmitted to the floor through the end pin of the bass, and (3) radiation efficiency of point-excited bending waves in the stage floor far below the coincidence frequency. Each aspect represents a prerequisite for the tuning fork–tabletop effect to take place. The input impedance at the end pin was measured for three representative double basses. The stage floors of five orchestra halls were measured with respect input impedance and damping, while sound radiation to the audience area was measured for two of them. In Lindeman Hall, Oslo, all conditions for the tuning fork–tabletop effect to take place were clearly met. The contribution from the stage-floor radiation to the sound pressure level in the audience area was found to be about 5 dB between 40 and 60 Hz, and even higher between 30 and 40 Hz.

The SMC Sound and Music Computing group at KTH (formerly the Music Acoustics group) is part of the Department of Speech Music and Hearing, School of Computer Science and Communication. In this short report we present the current status of the group mainly focusing on its research.

The study of the acoustics of bowed instruments has for several reasons focused on the violin. A substantial amount of knowledge has been accumulated over the last century (see Hutchins 1975, 1976; Hutchins and Benade 1997). The violin is discussed in Chap. 13, while the cello is discussed in Chap. 14. The bow is discussed in Chap. 16.

It is well known that plate radiation below the critical frequency is very poor, and therefore many stage floors dissipate low-frequency energy transmitted from double-bass and cello end pins rather than providing a tuning-fork/tabletop effect. However, if the stage floor is well damped, so that the transverse amplitudes fade out quickly around the point of excitation, a significant net radiation can be experienced also for low frequencies, due to the piston/baffle effect. Measurements performed in the Lindeman Hall of the Norwegian Academy of Music, in Oslo, Norway, showed that vibrational amplitudes in the stage floor faded out at a nearly equal pace in all directions around the excitation points, leaving nearly circular, quasi isotropic patterns for most frequencies of interest. In the audience area no tendency of spectral roll off was seen in the low-frequency end down to 30 Hz, which may represent the lowest fundamental of modern double basses. Transfer functions from stage floor to audience (intensity vs. power, and sound pressure vs. transverse velocity) were calculated for a number of seats in the hall.

This letter reports basic acoustic phenomena related to part-pedaling in the piano. With part-pedaling, the piano tone can be divided into three distinct time intervals: initial free vibration, damper-string interaction, and final free vibration. Varying the distance of the damper from the string, the acoustic signal and the damper acceleration were measured for several piano tones. During the damper-string interaction, the piano tone decay is rapid and the timbre of the tone is affected by the nonlinear amplitude limitation of the string motion. During the final free decay, the string continues to vibrate freely with a lower decay rate.

A sensor has been developed which allows measurement of the force exerted by the bow on the string ( bow force) during violin performance. The bow force is deduced from measurement of the transversal force at the termination of the bow hair at the frog. The principle is illustrated with an experiment that demonstrates how the bending of the stick and variations in bow hair tension influence the measurements. The design of the sensor is described and performance characteristics are discussed. A thorough calibration procedure is described and tested. Finally, the use of the sensor is demonstrated through measurements in real playing situations.

An experimental study of the upper and lower bow-force limits for bowed violin strings is reported. A bowing machine was used to perform bow strokes with a real violin bow on steel D and E strings mounted on a rigid monochord and on a violin. Measurements were systematically performed for 11 values of relative bow-bridge distance and 24 values of bow force at four bow velocities (5, 10, 15 and 20 cm/s). The measured string velocity signals were used to compile Schelleng diagrams, showing the distribution of different classes of string motion (multiple slipping, Helmholtz motion, raucous motion). It was found that the maximum bow-force limit for Helmholtz motion corresponded well to Schelleng's equation in modified form, taking the shape of the (hyperbolic) friction curve into account. The minimum bow force was found to be independent of bow velocity, which is in clear contradiction to Schelleng's prediction. Observations and simulations suggested that the breakdown of Helmholtz motion at low bow forces involves a mechanism related to ripple and corner rounding which was not taken into account in Schelleng's derivation of minimum bow force. The influence of damping showed only qualitative agreement with Schelleng's predictions.