Evaluation Of Loudness Research Articles

Methodological factors influencing loudness of short duration sounds

Three experiments were performed showing the relevance of methodological considerations to the apparent loudness of short duration equal-energy tone-bursts. In the first, the effect of slight modifications of the instructions on the results was shown. In the second the different results obtained with two techniques of loudness evaluation were studied. In the final experiment the difference in the loudness configuration of equal-energy tone-bursts evaluated by loudness estimation and loudness balance techniques was emphasized. With both techniques, however, a frequency-dependent critical duration was found.

Loudness Evaluations of the Sound from an Electric Clock

The noise from a consumer electric clock was studied to evaluate loudness estimating procedures. Eight different clock noises were tape recorded for presentation to a panel of people for loudness judgments. An electronic switch enabled the recorded clock noise and a 1000-Hz tone to be presented alternately via earphones for 12-sec durations with 12-sec silences in between signals. The person adjusted the 1000-Hz tone to match the loudness of the clock noise providing a correlation to the phon loudness scale. It was determined that Steven's method generally underestimates the loudness but is usually less than 10 dB in error. If ranking on a relative loudness scale is all that is desired, dB(A) measurements will suffice. [This work was supported by Westclox Division, General Time Corporation, LaSalle, Illinois.]

Loudness Balances Employing Signals with Unequal Duty Cycles

The alternate binaural loudness balance technique was employed to investigate the effects of duty cycle (the percentage of time the sound is on) upon the perceived magnitude of 1000-Hz pure-tone signals. The reference signal was fixed in the right ear at 50-dB sound-pressure level (SPL). In the left ear, the comparison signal intensity was adjusted via a Békésy audiometer to yield equal interaural loudnesses. The loudness of interrupted signals increased as the signal duty cycle was increased. A low-duty-cycle comparison signal was consistently judged to be softer than an equally intense high-duty-cycle reference signal. Furthermore, a high-duty-cycle comparison signal was consistently judged louder than a low-duty-cycle reference signal of the same intensity. The greatest interaural loudness disparity was observed for the experimental conditions in which the interaural duty-cycle difference (high duty cycle minus low duty cycle) was 80%. During a substantial number of trials, this relationship between duty cycle and loudness increased in magnitude throughout the 4-min balancing period. Duty-cycle-loudness effects were enhanced when a 400-msec silent interval separated alternating tones. The results of this study may be incorporated to assist in the explanation of the occurrence of the type-V Békésy pattern in clinical audiology. In addition, they lead to questions concerning the interpretation of experiments in which interrupted signals are presented for loudness evaluation such as experiments on loudness adaptation.

Loudness and annoyance of impulsive office noise

A study has been made on the evaluation of natural impulsive noises by subjective and objective procedures. One special example was used to get an indication of whether existing objective calculation methods might give sufficient agreement with subjective tests. The office noise sample studied bursts from a single typewriter operated at repetition rates between 1.5 and 15 strokes per second. A forced-pair comparison procedure of the constant stimulus type was used for the subjective evaluation. This choice has been prompted by the good results which we obtained with a corresponding method for speech quality measurements. In the subjective tests reported here, we asked for loudness and for annoyance comparisons. Two types of broad-band noise were utilized as reference signals. In addition to this, narrow-band noise centered at 1000 Hz was used to calibrate the two broad-band noises subjectively, and was also compared directly to the test noise. The subjective measurement results of this study are compared with those obtained by several well-known objective methods for noise rating and loudness evaluations.

Loudness and Annoyance of Impulsive Office Noise

A study has been made on the evaluation of natural impulsive noises by subjective and objective procedures. One special example was used to get an indication of whether existing objective calculation methods might give sufficient agreement with subjective tests. The office noise sample studied bursts from a single typewriter operated at repetition rates between 1.5 and 15/sec. A forced-pair comparison procedure of the constant stimulus type was used for the subjective evaluation. This choice has been prompted by the good results that we obtained with a corresponding method for speech quality measurements. In the subjective tests reported here, we asked for loudness and for annoyance comparisons. Two types of broad-band noise were utilized as reference signals. In addition to this, narrow-band noise centered at 1000 Hz was used to calibrate the two broad-band noises subjectively, and was also compared directly to the test noise. The subjective measurement results of this study are compared with those obtained by several well-known objective methods for noise rating and loudness evaluations.

Importance of Noise-Spectrum Measurements for Noise Control in Railway Vehicles

The authors have been working on noise control in railroad cars and engines. The key problem is the loudness evaluation of the typical broad-band railway noise with sufficient accuracy. However, it was found that the absolute value of the loudness level is of less importance than the difference between two noises—e.g., any improvement caused by some sort of acoustical adaptation, the increase of loudness level owing to higher moving speeds, the separation of the noise into single components, etc. For this purpose, direct measurements with the sound-level meter are simple, but so crude that sometimes they even contradict the subjective impression of loudness. Loudness calculations based on spectrum data give much better results. Results of loudness measurements and calculations for typical railroad noises are given. The differences between some of the usual loudness measures are outlined, and some conclusions with regard to noise control are discussed.