Discrimination of just noticeable change in pitch has been widely investigated. In contrast, works on discrimination of two simultaneous pitches produced by two tones have been scarce. In this work two methods were used to nd the minimum frequency interval in a two-tone at which listeners perceive two distinct pitches. In the rst, listeners tuned manually the frequency interval between components in a two-tone. In the second, the frequency interval between tones in a two-tone was switched between ve dierent xed values, and a pitch of a probe tone was compared with pitches in a two-tone. Both methods were used in two dierent groups of listeners, musicians and non-musicians. The rst method yielded substantially narrower intervals. Both methods revealed that musicians were able to discriminate pitches at narrower intervals than non-musicians. The raw results of tests were evaluated by two approaches, one was based on tting of the psychometric function and the other on statistical tests.

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The paper discusses the problem of thermal state of three-way catalytic converter depending on engine load with spark ignition fueled with gasoline and natural gas. The measurements on the test bench were performed, during which the temperature of the exhaust gases in the exhaust system was measured with the help of thermocouples, and at the same time, the track of the thermal state of the catalytic converter was monitored using thermo-vision camera. The stable work of engine with different rotation speed and values of load was considered together with transient states. The results of the measurements were presented in forms of charts and selected thermograms, qualitatively presenting the issue of thermal state of the catalytic converter.

Signal processing methods make possible such a mixing of signals that their overlapping in the time-frequency plane is reduced. This can be achieved by reducing the number of overlapping signals by discarding contributions from weaker signals and leaving only contributions from stronger ones. When applied to acoustic signals, this is referred to by the authors as selective mixing of sounds. Previous research has shown, that this rule, when applied to signals of musical instruments can provide some perceptual advantages over simple adding up the sound sources. In this paper, an experiment was carried out to determine the threshold of the value of relative energy of sound sources to control the decision about discarding a contribution from a particular sound source.

Sound synthesis methods based on physical modelling of acoustic instruments depend on data that require measurements and recordings. If a musical instrument is operated by a human, a difficulty in filtering out variability is introduced due to a lack of repeatability in excitation parameters, or in varying physical contact between a musician and an instrument, resulting in the damping of vibrating elements. Musical robots can solve this problem. Their repeatability and controllability allows studying even subtle phenomena. This paper presents an application of a robot in studying the re-excitation of a string in an acoustic guitar. The obtained results are used to improve a simple synthesis model of a vibrating string, based on the finite difference method. The improved model reproduced the observed phenomena, such as the alteration of the signal spectrum, damping, and ringing, all of which can be perceived by a human, and add up to the final sound of an instrument. Moreover, as it was demonstrated by using two different string plucking mechanisms, musical robots can be redesigned to study other sound production phenomena and, thus, to further improve the behaviours of and sounds produced by models applied in sound synthesis.