بررسی تطبیقی درجه‌بندی سنتی با خواص آکوستیکی حقیقی چوب گردو جهت سنتور‌سازی*

نوع مقاله: مقاله پژوهشی

نویسندگان

1 1کارشناسی ارشد مهندسی علوم و صنایع چوب و کاغذ، دانشکده منابع طبیعی، دانشگاه تهران، تهران

2 دانشیارگروه مهندسی علوم و صنایع چوب و کاغذ، دانشکده منابع طبیعی، دانشگاه تهران، تهران

3 دکتری مکانیک درخت و چوب، دانشگاه مونپلیه 2، مونپلیه، فرانسه

4 محقق و عضو گروه مکانیک درخت و چوب، در دانشگاه مونپلیه 2، مونپلیه، فرانسه

چکیده

چکیده
سال­هاست که چوب گردو به عنوان بهترین چوب و تنها منبع شناخته شده برای ساخت سنتور به کار می­رود. با وجود اینکه سازندگان ساز بنا بر تجارب شخصی، دیدگاه­های متفاوت و مشخصی در رابطه با خواص و کاربرد این چوب برای ساخت ساز دارند، تا به حال به ­طور علمی در این­باره کاری انجام نشده است. بنابراین در این تحقیق نمونه­های چوب گردوی سنتور­سازی با درجه­بندی­های سنتی مختلف، از کارگاه دو استاد سازنده ساز جمع­آوری و خواص صوتی واقعی آنها آزمون و مقایسه شد. چوب گردو خواص کلی سازهای زهی مضرابی را نشان داد: مدول ویژه بالا و ضریب میرایی نسبتاً کمتر. نمونه­های با درجه­های بالاتر دانسیته و مدول یانگ بالاتری داشتند. در تمام نمونه­ها، رابطه­ی کاهشی استاندارد میان ضریب میرایی و مدول ویژه مشاهده شد. نتایج آزمون­های صوتی، درجه­بندی تجربی اساتید را تأیید کرد: داده­های درجات بالا و پایین با هم اختلاف مشخصی را داشتند اما خط مرزی درجات میانی مبهم­تر بود و اهمیت برش، طرح صفحه رویی و رنگ در درجه­بندی سنتی را خاطر نشان کرد. تیمار­های سنتی بر بهتر شدن ویژگی­های چوب نهایی اثر مثبتی داشتند: تیمار بخار­دهی خصوصیات نمونه را به نمونه­ی با بالاترین درجه نزدیک کرد، همچنین چوب پیر­تر خواص ارتعاشی مناسب­تری را نشان داد.  

کلیدواژه‌ها


عنوان مقاله [English]

A Comparative Study between the Traditional Ratings and Real Acoustical Properties of Walnut Wood (Juglans regia) used in Santur Making*

نویسندگان [English]

  • Seyedeh Zahra Sharifi Soosari 1
  • Kambiz Pourtahmasi 2
  • Aida Se Golpayegani 3
  • Iris Brémaud 4
1 Master Degree in Engineering in Wood and Paper Science Technology, faculty of Natural Resources, University of Tehran, Tehran, Iran.
2 Associate Professor, Department of Wood Sicence and Technology, Faculty of Natural Resources, , University of Tehran, Tehran, Iran
3 PhD Holder in Mechanic of Tree and Wood, University of Montpellier II, Montpellier, France
4 Resercher in Civil Engineering, Department of Mechanic of tree and wood, University of Montpellier II, Montpellier, France.
چکیده [English]

Abstract:
For many years, the wood of walnut tree (Juglans regia) has been used for making Santur. Even though artisans have their own divers’ ideas about this species’ features; until now there has been no scientific data to support them. In Santur’s case specially, differently cut surface plates can be formed into final instrument. Besides, some steam treatments, which supposedly improve the final sound quality, are common for preparing the raw material. Their true efficiency is also unknown. In this study, specimens from Sanoor’s surface plates with different traditional grading were collected from ateliers of two professional instrument makers and their real vibrational properties were measured and compared. Different cutting plans, visual characteristics, the types of pretreatments involved as well as the sample’s age and conditions were the basis of grading according to artisans. Samples were dried and stabilized in a climatic chamber before being tested for their vibrational qualities. The vibration test was done using a non contact free-free bar bending method. The frequency sweep was between 100 and 500 Hz and both specific elastic modulus (E/ρ) – from the first frequency resonance using Euler-Bernoulli method– and damping coefficient (tanδ) –using bandwidth at the half power– were calculated. Walnut wood had the basic characteristics of chordophones related species: high specific modulus and comparatively low damping coefficient. No statistically significant difference was observed between the four obtained mechanical factors (i.e. Density, Young modulus, specific modulus and damping) based on the wood conditions (Heartwood or sapwood). However the traditional grading was related to the measured characteristics. The best graded specimens had both higher densities and Young moduli. In all specimens the standard decreasing relation between damping coefficient and specific modulus was observed. This verified the trustworthiness of the calculated data. As a general fact, the results of acoustical tests were in harmony with the grading. This means that the better graded samples had relatively higher specific moduli and lower damping coefficients. The situation was vice versa for the lowest grades. The line separating the best and the worst graded specimens was very clear, on the other hand middle range grades borderlines were vague, meaning all the measured factors were almost in the same range. This indicated the importance of artisanal cut, wood color and design in traditional grading: one acoustically valuable specimen could be cast aside just because it is not properly cut. Steaming as a commonly done traditional pretreatment had improving effects on the wood’s final characteristics: it apparently caused the specimen properties to get closer to the best graded ones. An old wood can also be considered a treated specimen, as aging can also be done artificially (by the hands of the craftsmen through leaving the wood untouched for years before beginning the process of fabrication) or naturally (as in direct using of an old tree). Walnut aged specimen, also demonstrated nearly the best mechanical features, validating the choice of the instrument makers in preferring the aged wood over the freshly cut one. In conclusion, in the case of Santur, a significant coherence between artisanal experimental knowledge and scientific data was observed

کلیدواژه‌ها [English]

  • Keywords: Walnut Wood (Juglans Regia)
  • Santur
  • Acoustical Characteristics
  • Damping
  • Steam Treatment
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