从物理看乐音的和谐(续)--物理与音乐专题之一

研究表明，人类的耳朵除了对基频外，较易听辨的就是二倍(频率)音、三倍音和四倍音．所以当一个基频为f1：f2：f3=400：500：600的三个音同时发声时，各音的二次谐频，三次谐频，四次谐频被加强，听感就变得和谐、明亮．而频率比不是简单整数比关     

电声音乐中的物理学问题--物理与音乐专题之六

一般而言，在电声乐器中，电声乐器与电子乐器不是一个概念．用传统的乐器发声，然后用电声放大的称为电声乐器，如电吉他、电扬琴、电子手风琴等．由电子振荡器产生声的称为电子乐器，如电子琴、电子钢琴等．数字式电子音响合成器也是电子乐     

室内音质设计的物理原理及应用--物理与音乐专题之五

无论是乐器还是喉咙发出的音乐声，总要经过传播才能被人听到．声波在空气中传播当然以直线传播为主，但反射和衍射不可避免的存在，而且对音乐的效果有重要影响．音乐在旷野、山颠、院落或室内，听起来强度和音色各不相同，无论是听者还是演唱者，感受都大不一样，可见环境对乐音的响度或音色是有影响的，这里的区别主要是反射的效果．     

打击乐器和膜、棒、板的振动--物理与音乐专题之四

藉助捶打、敲击、抓奏、刮奏、摇奏、弹拨等方法几乎可以使任何刚性物体发声．打击乐器就是利用这种方式发出乐音的乐器．它们大致可以分为两类：一类是有调打击乐器如木琴、钟琴、钢板琴、定音鼓和中国编钟等，此类乐器有音阶的变化，可以独立表演乐曲；另一类是无调打击乐器，如各种鼓、     

让学生看到音乐的数理之美--通过“乐音研究”再谈大学文科物理实验的设计与实施

针对新开设的大学文科物理实验“乐音研究”实验教学实践,着重强调了实验的设计理念、目的和思路。通过“乐音研究”实验,使文科学生区分噪音和乐音差异,了解其作为一种特殊力学振动的时域特征、频域特征,理解乐音“听起来好听”的悦耳和谐原理,并通过展示各个音符间的关系,让学生学会示波器以及LabView 分析界面的使用,通过分析归纳出“十二平均律”,最后利用“三分损益”方法构建管箫,体验音乐中包含物理学和数学在内的科学原理。     

胡琴的发声及其声波的辐射--物理与音乐系列专题之七

胡琴的历史悠久，早在唐代就已出现，称为奚琴，用竹片摩擦琴弦发声，是当时北方少数民族奚族的拉弦乐器．在宋代就有了胡琴的名称出现，北宋沈括在《梦溪笔谈》中有一首军士歌，“马尾胡琴随汉车，曲声犹自怨单于”．此歌明确记载当时已有马尾胡琴．在宋、元时代，胡琴被广泛用于器乐合奏，明、     

从X射线的发现看科学研究的偶然性与必然性--纪念伦琴发现X射线110周年

物理学史上有许多重大的发现、发明创造是科学家们在“无意”中发现的，其中颇为著名的是德国物理学家伦琴于1895年11月8日在德国维尔茨堡大学实验室，研究阴极射线时意外地发现了一种新的射线——X射线。X射线的发现立刻引起了全世界科学界的关注和轰动，并掀起了一股X射线研究热潮，并促使了天然放射性现象与电子等一系列重大发现的接踵而来，从而揭开了人类研究微观世界的序幕。乃至人们把X射线的发现称之为第二次科学革命的号角，现代物理学革命和现代科学革命的起点．对于如此重大的科学发现，其背后隐藏着的偶然性与必然性，值得我们深思。     

Intrusive sounds

The aim of this paper is to propose measures of intrusiveness of sound. Intrusiveness is understood here as that feature of sound which determines a high degree of annoyance in spite of the low value of noise rating. The paper discusses existing noise ratings and shows that they do not give satisfactory results as applied to sounds estimated as irritating or unpleasant. It is proposed that noise ratings should be extended to cover measures of intrusiveness.     

物理竞赛中的物理图象

图象处理法是物理竞赛中常用的处理方法,主要表现在图象的"面积"与图象的交点两个方面.     

Overlapping of sounds in piano passages

It is well known that, in piano passages, specifically, in those played legato, sounds may overlap in time. Our experiments show that this overlapping is much greater than one would expect proceeding from the undistorted pitch perception in a given phrase. Moreover, the sounds produced by piano and perceived by a listener as clearly distinguished in pitch, when subjected to an objective analysis, may prove to be a mixture of equally intense components of the preceding and next sounds. This phenomenon is related to the problem of piano quality, including the still unclarified role of the damper system, as well as to the mysterious manifestation of pianist’s personality that is called the art of touch.     

Theory of heart sounds

A phenomenological theory of heart sounds is proposed. The left ventricular wall is modelled as an incompressible spherical shell and the heart valves as two-dimensional membranes. The solutions of the appropriate elasticity equations are matched with those of the hydrodynamical equations describing the propagation of the radiated sound through the soft body tissue. The predicted time plots and frequency spectra show significant resemblance with recorded ones, like equidistant peaks, directional dependence, relationship of sound amplitude and rate of pressure change inside the left ventricle, etc. Sets of parameters are singled out which influence the measured sound. The latter is the integral part of a diagnostic procedure.     

Physics Without Physics

David Finkelstein was very fond of the new information-theoretic paradigm of physics advocated by John Archibald Wheeler and Richard Feynman. Only recently, however, the paradigm has concretely shown its full power, with the derivation of quantum theory (Chiribella et al., Phys. Rev. A 84:012311, 2011; D’Ariano et al., 2017) and of free quantum field theory (D’Ariano and Perinotti, Phys. Rev. A 90:062106, 2014; Bisio et al., Phys. Rev. A 88:032301, 2013; Bisio et al., Ann. Phys. 354:244, 2015; Bisio et al., Ann. Phys. 368:177, 2016) from informational principles. The paradigm has opened for the first time the possibility of avoiding physical primitives in the axioms of the physical theory, allowing a re-foundation of the whole physics over logically solid grounds. In addition to such methodological value, the new information-theoretic derivation of quantum field theory is particularly interesting for establishing a theoretical framework for quantum gravity, with the idea of obtaining gravity itself as emergent from the quantum information processing, as also suggested by the role played by information in the holographic principle (Susskind, J. Math. Phys. 36:6377, 1995; Bousso, Rev. Mod. Phys. 74:825, 2002). In this paper I review how free quantum field theory is derived without using mechanical primitives, including space-time, special relativity, Hamiltonians, and quantization rules. The theory is simply provided by the simplest quantum algorithm encompassing a countable set of quantum systems whose network of interactions satisfies the three following simple principles: homogeneity, locality, and isotropy. The inherent discrete nature of the informational derivation leads to an extension of quantum field theory in terms of a quantum cellular automata and quantum walks. A simple heuristic argument sets the scale to the Planck one, and the currently observed regime where discreteness is not visible is the so-called “relativistic regime” of small wavevectors, which holds for all energies ever tested (and even much larger), where the usual free quantum field theory is perfectly recovered. In the present quantum discrete theory Einstein relativity principle can be restated without using space-time in terms of invariance of the eigenvalue equation of the automaton/walk under change of representations. Distortions of the Poincaré group emerge at the Planck scale, whereas special relativity is perfectly recovered in the relativistic regime. Discreteness, on the other hand, has some plus compared to the continuum theory: 1) it contains it as a special regime; 2) it leads to some additional features with GR flavor: the existence of an upper bound for the particle mass (with physical interpretation as the Planck mass), and a global De Sitter invariance; 3) it provides its own physical standards for space, time, and mass within a purely mathematical adimensional context. The paper ends with the future perspectives of this project, and with an Appendix containing biographic notes about my friendship with David Finkelstein, to whom this paper is dedicated.