using System; using L=Science.Physics.GeneralPhysics; namespace Serway.Chapter18 { /// /// Example06: Wind in a Culvert /// A section of drainage culvert 1.23 m in length makes a /// howling noise when the wind blows. /// (A) Determine the frequencies of the first three harmonics /// of the culvert if it is cylindrical in shape and open at /// both ends. Take v = 343 m/s as the speed of sound in air. /// f_1 = 139 Hz /// f_2 = 278 Hz /// f_3 = 417 Hz /// (B) What are the three lowest natural frequencies of the /// culvert if it is blocked at one end? /// f_1 = 69.7 Hz /// f_3 = 209 Hz /// f_5 = 349 Hz /// (C) For the culvert open at both ends, how many of the /// harmonics present fall within the normal human hearing /// range (20 to 20000 Hz)? /// n = 143 /// public class Example06 { public Example06() { } private string result; public string Result { get{return result;} } public void Compute() { double v = 343.0; double L = 1.23; //(A) // v = lambda_n*f_n // lambda_n = 2*L/n // f_n = v/2/L*n result+=Convert.ToString(v/2/L*1)+"\r\n"; result+=Convert.ToString(v/2/L*2)+"\r\n"; result+=Convert.ToString(v/2/L*3)+"\r\n"; //(B) // v = lambda_n*f_n // lambda_n = 4*L, 4*L/3, 4*L/5 // f_n = v/4/L*n result+=Convert.ToString(v/4/L*1)+"\r\n"; result+=Convert.ToString(v/4/L*3)+"\r\n"; result+=Convert.ToString(v/4/L*5)+"\r\n"; //(C) double number = (20000-20)/(v/2/L*1); result+=Convert.ToString(number)+"\r\n"; } } } /* 139.430894308943 278.861788617886 418.292682926829 69.7154471544715 209.146341463415 348.577235772358 143.296793002915 */