ALUMINIJSKA AKUSTIČNA GITARA

KOMPARATIVNE PREDNOSTI I MANE ALUMINIJSKE AKUSTIČNE GITARE NASPRAM KLASIČNE DRVENE

Sažetak: Napravljen je i ispitan prototip akustične aluminijske gitare. Izvršeno je mjerenje fizikalnih veličina: buka, dužina trajanja zvuka, težina i volumne zapremnine akustičnog dijela gitare. Dobiveni rezultati su usporedivi i pružaju mogućnost serijske izrade jeftinijih i trajnijih aluminijskih gitara. Aluminijska gitara cijenom i trajnošću predstavlja optimalan izbor za prvu kupnju i vježbanje.

1. Uvod: Obzirom da je drvo izolator, a metal vodič u ovom radu napravljena je usporedba kako izbor materijala utječe na jačinu zvuka, ali i “boju zvuka” akustične gitare. Napravljen je prototip akustične aluminijske gitare kako bi se mogle uspoređivati dobivene vrijednosti na prototipu i klasičnoj drvenoj gitari.

2. Izbor parametara:

  • a. Težina u kilogramima (kg) je mjerena na obe gitare vaganjem.
  • b. Volumen akustičnog dijela gitare izražen je u litrama (l).
  • c. Trajanje zvuka izraženo je u sekundama (s), a u tu svrhu korišten je stetoskop i štoperica.
  • d. Buka (jakost zvuka) je izražena u decibelima (dB), a mjerena je sa fonometrom.
  • e. Boja zvuka ocjenjena je na temelju slobodne procjene muzičara.

3. Esperimentalni dio: Upotrebljene su dvije gitare te izmjereni parametri opisani pod točkom 2. Klasična, akustična, drvena gitara (Španjolka-Raimundo) proizvedena je i kupljena u Španjolskoj 1974 godine. Prototip aluminijske, akustične gitare napravljen je 2002 godine. Materijal za izradu akustičnog dijela gitare je aluminijska legura ALMg 2. Odabrana je legura koja se dobro zavaruje, a otporna je i na koroziju (morska voda). Debljina lima je 1,5 mm, a lim je zavaren TIG postupkom u zaštiti plina argona i uz izmjeničnu struju. Graditelj i dizajner akustične aluminijske gitare je i autor ovoga rada.

Volumen akustičnog dijela aluminijske gitare izmjeren je tako da se u gitaru ulijevala voda iz menzure. Volumen akustičnog dijela drvene gitare nije se mogao mjeriti na takav način nego se je tlocrtno i po visini usporedio sa aluminijskom gitarom.

Trajanje zvuka mjereno je tako da se je osjetnik stetoskopa zalijepio na akustični dio gitare. Aktiviranjem dura E mjerilo se na štoperici koliko je vremena u sekundama potrebno da nastupi tišina.

Buka ili jakost zvuka mjerena je pomoću fonometra (tip-FM 120). Uređaj se postavio na udaljenost od 100 milimetara od žica na perforiranom dijelu gitare. Aktiviranjem dura E mjerena je jakost zvuka izražena u decibelima (dB).

Parametri Drvena Gitara Aluminijska Gitara
Težina (kg) 1,265 2,540
Volumen (l) više od 10,35 10,35
Trajanje zvuka (s) 9,5 11,4
Jakost zvuka (dB) 102 121

Tablica 1. Rezultati mjerenja

Procjena boje zvuka spada u individualnu kategoriju. Ljudsko uho je za tu procjenu najbolji instrument. Taj kriterij najbolje mogu ocijeniti i procijeniti muzičari. Mišljenje muzičara je da se akustična aluminijska gitara može dobro podešavati te da daje čisti, jasni i reski zvuk. Soliranje na gitari je dojmljivo i razlikuje se u pozitivnom smislu od drvene gitare. Mijenjajući gitare prilikom sviranja u cilju testiranja osjećaja punoće prostora ispunjenog zvukom muzičari daju prednost drvenoj gitari.

4. Zaključak: Dobiveni rezultati testiranja obe gitare su usporedivi. Aluminijska gitara je osjetno teža ali se može i smanjiti, jer je znatno ojačana. Volumen drvene gitare je veći, a jakost zvuka je manja uspoređujući sa aluminijskom gitarom. Za jednaku jakost zvuka aluminijsku gitaru bi mogli napraviti tanju, a time i lakšu. Drvena gitara se vremenom suši i puca pa je podložna dodatnim troškovima u cilju održavanja. Otpornost na udarce bolje podnosi aluminijska gitara. Tehnološki gledano aluminijska gitara se može jeftinije i jednostavnije proizvesti od drvene. Industrijski i ljudski potencijali u našoj zemlji za izradu aluminijskih akustičnih gitara postoje. Aluminijska gitara cijenom i trajnošću može predstavljati dobar izbor za prvu kupnju i vježbanje.



COMPARATIVE ADVANTAGES AND WEAK POINTS OF AN ALUMINIUM ACOUSTIC GUITAR COMPARED TO A CLASSIC WOODEN GUITAR

Abstract: A prototype of an acoustic aluminum guitar has been made and tested. Measuring has been done of physical parameters: noise, duration of the sound, weight, volume capacity of the acoustic part of the guitar. The results are comparable and offer the possibility of serial production of cheaper and more durable acoustic aluminum guitar. Due to the price and long life the aluminum guitar is the optimal choice for the first buy and practicing.

1. Introduction: Since wood is an isolator and metal a conductor a comparison was made to see how the choice of material affects the intensity and timbre of sound of an acoustic guitar. A prototype of an acoustic aluminum guitar was made in order to compare the received values on the prototype and on the classic wooden guitar.

2. Chice of paramertars:

  • a. weight in kilograms (kg) was measured by weighing both guitars
  • b. volume of the acoustic part of the guitar is expressed in liters (l)
  • c. duration of sound is expressed in seconds (s) and stethoscope and stop-watch were used to measure it
  • d. noise (intensity of sound) is expressed in decibels (dB) and it was measured with an instrument
  • e. timbre of sound was evaluated on the basis of musicians' opinions

3. Esperimental part: Two guitars were used and parameters mentioned under 2. were measured. The classic acoustic wooden guitar (Spanish-Raimundo) was manufactured and acquired in Spain in 1974. The prototype of the aluminum acoustic guitar was made in 2002. The material used to make the the acoustic part of the guitar is an aluminum alloy AlMg2. The chosen alloy is easy to weld and is resistant to corrosion (sea water). The thickness of the metal sheet is 1,5 mm and the metal sheet was welded using the TIG technique in argon protection and with alternating current. The builder and the designer of the acoustic aluminum guitar is at the same time the author of this paper.

The volume of the acoustic part of the guitar was measured by pouring water from a measured in the same way, so its sketches and height were compared to those of the aluminum guitar.

The duration of the sound was measured in a way that the receptor of the stethoscope was stuck to the acoustic part of the guitar. After activating the E major the time necessary to achieve complete silence was measured with a stop-watch in seconds. The noise or intensity of the sound was measured with instruments. The instrument was installed at a distance of 100 millimeters from the strings on the perforated part of the guitar. After activating the E major, the intensity of the sound was measured in decibels (dB).

Parameters Wooden Guitar Aluminum Guitar
Weight (kg) 1,265 2,540
Volume (l) more than 10,35 10,35
Duration of sound (s) 9,5 11,4
Intensity of sound (dB) 102 121

Table 1. Measuring resuts

The estimation of the timbre is an individual category. Human ear is the best instrument for such estimation. Musicians are the most qualified it. The opinion of the musicians is that the aluminum guitar can be fine-tuned and that its sound is pure, clean and sharp. The solo on the guitar is in their opinion impressive and it differs in a positive way from the wooden guitar. Musicians switched guitars while playing in order to test the sense of fullness of the room filled with the sound and they all give preference to the wooden guitar.

4. Conclusion: The received results of testing both guitars are comparable. The aluminum guitar is noticeably heavier but it can be downsized because it is now considerably strengthened. The volume of the wooden guitar is bigger and the intensity of the sound is weaker compared to the aluminum guitar. Without altering the intensity of the sound, the aluminum guitar could be made thinner and thus also lighter. The wooden guitar dress in time and cracks and is liable to additional maintenance costs. The aluminum guitar can be produced more easily and at a lower cost than the wooden one. There are industrial and human resources in our country for producing acoustic guitars. Due to the price and durability the aluminum guitar can be the best choice for the first purchase and practicing.

Autor inovacije: Srećko Brkić,dipl.inž.stroj.(EWE)
Ilica 322, 10 000 Zagreb (mob. 091/2532636). E-mail sreckobrkic@net.hr