Sound Frequency Spectrum Research Articles

Sound influence on landscape values

In order to study the influence of the interaction between visual and acoustic stimuli on perception of the environment, 36 sound and image combinations were presented to 75 subjects. The sounds and images used were of natural and semi-natural settings and urban green space. Affective response was measured in terms of pleasure. The results show a rank of preferences running from natural to man-made sounds, with the nuance of a potential alert or alarm-raising component of the sound. The potential for alert or alarm-raising may be related, over and above the information content or meaning, to the characteristics of the sound frequency spectrum, specifically to the existence of frequency bands whose sound levels impose themselves on the acoustic background. The congruence or coherence between sound and image influences preferences. Coherent combinations are rated higher than the mean of the component stimuli. Results suggest that there is a need to identify places or settings where the conservation of the sound environment is essential, because of its salient informational content or due to the drastic impact of the loss of sound quality on observer appreciation, for example, in urban green spaces, natural spaces and cultural landscapes.

Sound frequency analysis and the site of snoring in natural and sedation-induced sleep

Frequency analysis of snoring sounds has been shown to correlate with the site of upper airway narrowing. The aim of this study was to compare the sound frequency spectra of snores generated during induced snoring at sleep nasendoscopy with those during natural sleep. The sound of 11 subjects snoring overnight and during sleep nasendoscopy was digitally recorded. The observed site of vibration was noted for each snore sample recorded at sleep nasendoscopy. A Fast Fourrier Transformation was used to produce frequency spectra. At sleep nasendoscopy observed palatal snores (76) had a median peak frequency at 136 Hz, tongue based snores (10) at 1243 Hz and simultaneous palate and tongue (six) at 190 Hz. The median power ratios (defined as the area under the frequency spectra below 750 Hz/area above 750 Hz) were 33 for palatal snores, 0.2 for tongue base snores and 5 for simultaneous palate and tongue. Natural snores (275) had a dominant median peak at 132 Hz with a ratio of 88. A comparison of overnight snores (200) of those subjects (eight) with observed palatal snores (76) was made. Neither the peak frequency nor power ratio of natural and induced snores were significantly different (P = 0.85 and P = 0.13, respectively). The power ratio in four of the subjects individually was significantly different (P < 0.05). These results suggest that sedation-induced snores contain a high frequency component consistent with an element of tongue base snoring, not evident in natural snores. Thus sleep nasendoscopy may not accurately reflect snoring during natural sleep. Sound frequency analysis during natural sleep may therefore be a better predictive investigation for the success of palatal surgery.

Sound frequency analysis and the site of snoring in natural and sedation induced sleep

Frequency analysis of snoring sounds has been shown to correlate with the site of upper airway narrowing. The aim of this study was to compare the sound frequency spectra of snores generated during induced snoring at sleep nasendoscopy with those during natural sleep. The sound of 11 subjects snoring overnight and during sleep nasendoscopy was digitally recorded. The observed site of vibration was noted for each snore sample recorded at sleep nasendoscopy. A Fast Fourrier Transformation was used to produce frequency spectra. At sleep nasendoscopy observed palatal snores (76) had a median peak frequency at 136 Hz, tongue based snores (10) at 1243 Hz and simultaneous palate and tongue (six) at 190 Hz. The median power ratios (defined as the area under the frequency spectra below 750 Hz/area above 750 Hz) were 33 for palatal snores, 0.2 for tongue base snores and 5 for simultaneous palate and tongue. Natural snores (275) had a dominant median peak at 132 Hz with a ratio of 88. A comparison of overnight snores (200) of those subjects (eight) with observed palatal snores (76) was made. Neither the peak frequency nor power ratio of natural and induced snores were significantly different (P = 0.85 and P = 0.13, respectively). The power ratio in four of the subjects individually was significantly different (P < 0.05). These results suggest that sedation-induced snores contain a high frequency component consistent with an element of tongue base snoring, not evident in natural snores. Thus sleep nasendoscopy may not accurately reflect snoring during natural sleep. Sound frequency analysis during natural sleep may therefore be a better predictive investigation for the success of palatal surgery.

The Influence of Concrete Elastic Characteristics on the Impact Noise Insulation of Concrete Floors

The noise insulation characterisation of a bare floor for structure-borne sound is usually based on specific tests made in accordance with the established international standard EN ISO 20140 and the structure-borne noise insulation index calculated according to standard EN ISO 20717. For bare concrete floors of the same type, which one might suppose would have identical acoustical performance, different impact sound insulation frequency spectra may be obtained if the concrete at the zone where the impact hammer strikes is of different type. This situation is particularly the case for bare floors which have levelling layers of floor screeds. This work presents an analytical study of the influence of the elastic characteristics of the concrete used in the area of the bare floor where the hammer of the standard tapping machine strikes (whether it be the structural concrete of the slab or a light concrete screed applied as a levelling layer), on the impact noise insulation spectra, and on the corresponding value of the structure-borne sound insulation index. The study firstly involved theoretically modelling the applied impulsive force spectrum of the hammer impact. Secondly, the modelled force spectrum was compared with the results of impact characteristics obtained using several shock tests on defined specimens, for which the effective impact force is determined. Finally, using these resulting force spectra, some simulations on a standard floor were performed to determine the changes in the response spectra, and the corresponding insulation index for structure-borne sound. Some additional considerations and conclusions are also presented.

Effect of Vehicle Speed on Sound Frequency Spectra

During analysis conducted on data collected by the University of Central Florida for the Florida Department of Transportation (FDOT), which was doing research to develop reference energy mean emission levels for high-speed traffic, other interesting data trends became apparent. One such trend was the relationship of vehicle speed and sound emission spectra. The data base contained real-time one-third octave band data and vehicle characteristics (e.g., speed) and permitted a detailed review of sound emission spectra with respect to vehicle speed. The purpose of this research was to attempt to develop a mathematical relationship between increasing vehicle speed and sound emission spectra. Based on the results of this research several important conclusions were drawn: (a) a trend in the change in sound frequency spectra with respect to vehicle speed may exist for all vehicle types defined in STAMINA 2.0; (b) the change in dominant frequency followed no apparent trend with respect to vehicle speed; (c) the data base used for this research was too small for accurate mathematical modeling of the change in sound frequency versus vehicle speed; and (d) the sound attenuation provided by noise barriers may be underestimated using the current method of estimating barrier attenuation based on an effective frequency of 500 Hz regardless of vehicle speed.

Effect of Vehicle Speed on Sound Frequency Spectra

During analysis conducted on data collected by the University of Central Florida for the Florida Department of Transportation (FDOT), which was doing research to develop reference energy mean emission levels for high-speed traffic, other interesting data trends became apparent. One such trend was the relationship of vehicle speed and sound emission spectra. The data base contained real-time one-third octave band data and vehicle characteristics (e.g., speed) and permitted a detailed review of sound emission spectra with respect to vehicle speed. The purpose of this research was to attempt to develop a mathematical relationship between increasing vehicle speed and sound emission spectra. Based on the results of this research several important conclusions were drawn: (a) a trend in the change in sound frequency spectra with respect to vehicle speed may exist for all vehicle types defined in STAMINA 2.0; (b) the change in dominant frequency followed no apparent trend with respect to vehicle speed; (c) the data base used for this research was too small for accurate mathematical modeling of the change in sound frequency versus vehicle speed; and (d) the sound attenuation provided by noise barriers may be underestimated using the current method of estimating barrier attenuation based on an effective frequency of 500 Hz regardless of vehicle speed.

A comparison of noise measures for assessing vehicle noisiness

The control of vehicle noise is currently achieved by using the A-weighted sound pressure level and measuring the maximum sound level achieved during a full acceleration test. Doubts have been expressed about the continuing use of the scale of dB(A) as the sole means of assessing and regulating this noise, since it is felt that some vehicles emitting the same sound level when measured on the dB(A) scale can differ appreciably in terms of their subjective noisiness. This paper describes four experiments where the aim was to determine whether other noise scales would be more appropriate for measuring vehicle noise. A total of over 100 subjects made assessments of the noisiness of a wide range of recorded vehicle noises. The sounds were replayed in two listening rooms designed to simulate indoor and outdoor listening conditions. It was concluded that, generally, loudness measures were most closely related to average noisiness ratings, but provided that the frequency spectra of vehicle sounds are not greatly different, loudness measures have no advantage over the A-weighted level currently employed.

Frequency distribution of breath sounds as an indicator of bronchoconstriction during histamine challenge test in asthmatic children.

In order to study changes in respiratory sounds associated with acute bronchoconstriction and -dilatation, breath sounds of 11 children with asthma (age range, 10-14 years) were recorded at the chest and at the trachea during histamine challenge test and after subsequent bronchodilatation. The changes in frequency spectra of breath sounds were compared with simultaneous changes in forced expiratory volume in 1 second (FEV1). In seven children who responded to histamine with a decrease in FEV1 of more than 15%, there was a significant relationship between percentage change in FEV1 (delta FEV1) and percentage change in median frequency (delta F50) of expiratory breath sounds recorded at the chest (r = 0.865; beta = -0.706, P = 0.0001) and at the trachea (r = 0.888; beta = -1.12, P = 0.0001). The association between breath sound intensity and FEV1 was weaker. Based on ANOVA, the increase of F50 during the challenge test was significantly larger in children who responded to histamine than in those who were non-responsive (P = 0.0016). At the chest, a decrease of 15% in FEV1 corresponded to an increase of 8% in expiratory F50. The provocative dose of histamine inducing a decrease of 15% in FEV1 (PD15FEV1) and the provocative dose causing an increase of 8% in F50 (PD8F50) were significantly related (r = 0.927, P = 0.003). We conclude that spectral analysis of breath sounds can be used to indicate airway obstruction during bronchial challenge tests in children, and may be adapted for tests in pre-school children. The results suggest that the same mechanisms that induce airflow limitation due to inhaled histamine may generate an increase in frequency content of breath sounds in children with asthma.

Acoustic analysis of the closing sounds of bileaflet prosthetic valves in a sheep model

Previous investigations of mechanical valve sounds have shown that (1) frequency spectra of sounds produced by abnormal valves differ from those of properly functioning valves and (2) leaflets of normally functioning bileaflet valves do not close synchronously. This investigation studied effects of mechanical valve size, environment, and hemodynamic state on closing sounds. A single 25 mm bileaflet mitral mechanical valve was implanted in six sheep and a single 27 mm valve in four sheep. With digital signal processing, asynchronous leaflet closure and frequency spectra were assessed after alterations in animal position, respiratory phase, heart rate, afterload, contractility, and preload. Both asynchronous leaflet closure and frequency spectra varied among animals, and, except for a decrease in asynchrony with increasing contractility, were largely independent of valve size and hemodynamics. Baseline asynchrony ranged from 0.5 to 4.2 msec. Frequency spectra were characterized by the first three resonant peaks. Lowest resonant peaks ranged from 2.5 to 3.4 kHz, middle from 4.7 to 6.8 kHz, and highest from 7.2 to 9.6 kHz. These results indicate that accurate assessment of mechanical valve function with acoustic analysis requires baseline studies in all patients by means of a system with a frequency response of more than 10 kHz.

Noninvasive detection of coronary stenoses before and after angioplasty using eigenvector methods

Previous studies done by our group suggest that partially occluded coronary arteries may generate sounds due to turbulent blood flow. To support these previous findings the frequency spectra of diastolic heart sounds are compared before and after angioplastic surgery. Since the low-level sounds associated with partially occluded coronary arteries are contaminated with considerable background noise, traditional FFT analysis may not produce accurate frequency spectra. Indeed, in a previous study using the same data, no significant differences were found in the diastolic heart sounds before and after angioplastic surgery. In this study, three eigenvector methods (Pisarenko, MUSIC, and Minimum-Norm) have been selected to generate the frequency spectra because of their higher resolution, particularly in the presence of noise. Although the Pisarenko method produced spurious zeros and could not be used, the other two methods produced spectra showing, in most cases, a marked decrease in high-frequency spectral components following angioplasty.

Characteristics of normal lung sounds after adaptive filtering.

Lung sounds were recorded from five normal male subjects during tidal breathing. Simultaneous electrocardiograms were recorded and used as index signals to generate simulated heart sounds for digital subtraction from recorded lung sounds to obtain purer lung sounds. Five random breaths from each subject were analyzed. Sound signals were band-pass filtered 25 to 1,000 Hz (antialiasing), digitized at 3,000 Hz, and then subjected to (1) direct fast Fourier transform (FFT) without filtering (NF); (2) digital high-pass filtering at 75 Hz and subsequent FFT (75 HzF); (3) adaptive filtering and subsequent FFT (AF). The FFT algorithms of all lung sounds were characterized by mean, median, and mode frequencies. The mean, median, and mode of NF were lower than those of 75 HzF (64.98 +/- 4.04 versus 150.42 +/- 17.49, mean +/- SE, p less than 0.003; 44.57 +/- 2.06 versus 111.81.5.78, p less than 0.0003; 36.81 +/- 1.77 versus 86.16 +/- 3.13, p less than 0.0001) and those of AF (64.98 +/- 4.04 versus 96.87 +/- 11.58, p less than 0.01; 44.57 +/- 2.06 versus 68.23 +/- 10.44, p less than 0.05; 36.81 +/- 1.78 versus 52.24 +/- 8.97, p less than 0.06). The mean, median, and mode of AF were lower than those of 75 HzF (96.87 +/- 11.58 versus 150.42 +/- 17.49, p less than 0.02; 68.23 +/- 10.44 versus 111.81 +/- 5.77, p less than 0.007; 52.24 +/- 8.97 versus 86.16 +/- 3.73, p less than 0.01). The results indicated that by filtering out low frequency heart sounds, the frequency spectrum of lung sounds was moved upward.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlations between hearing and sound production in piranhas

In order to determine whether correlations exist between hearing and the known soundproduction abilities in piranhas (Serrasalmus nattereri), behavioral auditory thresholds were obtained with continuous tones and tone pulses. A new avoidance conditioning method was developed, where fin movements of caged animals were taken as response to a tone. The mean values of the far-field audiogram ranged from −26 dB re. 0.1 Pa at 80 Hz to a low point of about −43 dB between 220–350 Hz and rose to −14 dB at 1500 Hz. The frequency spectrum of typical drumming sounds (barks) covers the range of best hearing (100–600 Hz).

Effects of lung volume and airflow on the frequency spectrum of vesicular lung sounds

The purpose of this study was to determine whether the vesicular lung sound frequency spectrum is affected by changes in lung volume and airflow. Nine healthy young nonsmokers were studied. The dependent variables were the points that divided the power spectrum of the vesicular lung sound into quarters (1st, 2nd and 3rd quartiles (Q 1, Q 2 and Q 3)). Recording sites were the right upper anterior (RUL) and lower posterior (RLL) chest wall. Lung sounds were high-pass filtered at 100 Hz. To evaluate the effect of volume, lung sounds were recorded during an inspiratory vital capacity (VC) maneuver at near constant airflow rates. The spectral parameters were determined at each sixth of the VC. To assess the effects of airflow, 5 of the subjects breathed from resting lung volume at peak inspiratory airflows of between 1 and 3.0 L/sec for a total of 16 breaths each and the frequency parameters of the lung sounds occurring peak inspiratory airflows were determined. RESULTS: Volume effects: only at the RUL was there a small but significant decrease in all three parameters with increasing lung volume. Airflow effects: all parameters were independent of airflow except for a weakly positive relationship ( r=0.285, P<0.05) for Q 3 at the RUL location. Individually, there were weakly significant trends in three of the five subjects. These data suggest that the frequency composition of the vesicular lung sound in groups of healthy adults is not systematically affected by changes in lung volume or airflow.

Correlation of constant flow rate with frequency spectrum of respiratory sounds when measured at the trachea.

Respiration is one of the critical physiological functions of concern when a patient is under examination or treatment. A clinical relationship between respiratory sounds and gross respiratory pathology was established early in the 19th century by auscultation. It is commonly believed that characteristics of respiratory sounds are related to respiratory flow rate. The objective of this study is to determine the correlation or relationship between spectral composition of respiratory sounds as measured at the trachea and flow rates as measured by pueumotachometer. Respiratory sounds at six contant flow rates were measured with an electronic stethoscope placed at the anterior cervical triangle, inferior to the circoid cartilage. Results indicated that the mean frequency of the power spectrum increases linearly with increase in flow but remains about the same when the flow rate is above 0.75 I/s. In addition, the expiratory spectra have higher mean frequencies than inspiratory spectra.

Spectral analysis of heart sounds: Relationships between some physical characteristics and frequency spectra of first and second heart sounds in normals and hypertensives

Frequency analysis of heart sounds has been gaining recognition as a possible indicator of several heart and valve diseases, although a comprehensive study of normal heart sounds has not been published. Relating the frequency content of normal heart sounds to certain physical characteristics surrounding the generation of these sounds could lead to a valuable diagnostic tool and give a better understanding of the mechanism of heart sounds production. In this study, the first and second heart sounds from seventy-four normal, and seven hypertensive volunteers were recorded, digitized and analysed using a Fast Fourier Transform algorithm. Statistical analysis was used to relate physical characteristicss (sex, blood pressure, and body surface area) of the subjects to the frequency content of normal heart sounds and to compare normal and hypertensive heart sounds. Statistical analysis showed that the major concentration of energy, for both first heart sound (S1) and second heart sound (S2), is below 150 Hertz (Hz) which may indicate that both sounds are caused by vibrations within the same structure, possibly the entire heart. However S2 spectra have greater amplitude than S1 spectra above 150 Hz, which may be due to vibrations within the aorta and pulmonary artery. Relationships observed between body surface area, sex, blood pressure, and the frequency content of heart sounds indicate that as heart size increases, the amplitude of the frequency coefficients above 150 Hz decreases. These observations were more identifiable in the S1 spectra than in the S2 spectra, possibly because the S2 higher frequency components may mask subtle changes in the S2 spectra caused by heart size changes. However, when the changes in heart size are significant, as in hypertension or increased body surface area, trends in the S2 spectra can be observed.

Stridulatory structures and acoustic spectra of seven species of New Zealand wetas (Orthoptera: Stenopelmatidae)

Descriptions of fermoro-abdominal stridulatory structures and frequency spectra of stridulatory sounds are presented for 7 species ( Hemideina, Deinacrida) of Stenopelmatidae. In Hemideina, femoral pegs and abdominal file ridges were approximately similar in shape among species, but varied in size. The abdominal component differed in Deinacrida and consisted of either 1 or 2 heavy ridges, or an array of thin, upright, rectangular pegs. The stridulatory structures in some species had elaborate lips, grooves or buttresses. Acoustic spectra of defensive sounds of 3 Hemideina spp. had overlapping peaks between 4 – 14 kHz; a 4th species had a peak at 2 kHz. The spectral intensity dropped sharply above peak frequencies. Spectra for 3 Deinacrida spp. were very broad (1 – 90 kHz) with a shallow roll-off above peaks. The peak frequency band was 10 – 50 kHz. Each species had a different characteristic spectrum. There is no clear, consistent relationship between stridulatory structure size and spectral characteristics of stridulatory sounds.

Charcteristics and Control of Transformer Sound

This paper discusses some of the effects of material and processing upon the sound producing characteristics and the sound frequency spectrum of a power transformer. It also examines the sound conditions and frequency spectrum at various distances up to one mile (1.6 km) from the transformer

Auditory nerve and interneurone responses to natural sounds in several species of cicadas

ABSTRACT. The calling and courtship songs of 17‐year cicadas and of Say's cicadas differ both in the sound frequency spectrum and in temporal pattern. Multiunit recordings with hook electrodes from the whole auditory nerve show that the hearing organs are especially sensitive to transient stimuli occurring in natural sounds. Artificially produced clicks elicit bursts of spikes synchronized among various primary sensory fibres. These fibres respond to natural calling and courtship songs with a specificity dependent on carrier frequency, rhythm and transient content of the sound, following sound pulses (i.e. tymbal actions) up to repetition rates of 200 Hz. An ascending, plurisegmental interneurone was characterized by intracellular recording and simultaneously stained with cobalt. Its main arborization spatially overlaps the anterior part of the sensory auditory neuropile, and the axon was traced as far as the prothoracic ganglion. Direct input from primary auditory fibres was suggested by latency measurements. Intracellular recordings from such neurons in different species show distinct auditory input, with phasic‐tonic spike responses to tones. In general, the interneurone response is more species‐specific to calling than to courtship songs, and the preferential response to the conspecific calling song is based primarily upon sound frequency content.

Tegminal amplifiers and spectrum consistencies in Conocephalus nigropleurum (Bruner), Tettigoniidae

The sound frequency spectrum of Conocephalus nígropleurum (Bruner) was investigated with two different models of a custom-built analyser. The spectrum is continuous from 0 to 100 kc/s and contains a band of markedly more intense frequencies extending from 28 to 60 kc/s. When sufficient care was taken to eliminate variation due to microphone-insect alignment, this band or intensity aggregate was found to be highly consistent in the amplitude of its component frequencies. The proximal portions of the tegmina contain modified cells. Tearing these cells produced a large reduction in intensity over the entire spectrum but failed to alter the location and shape of the aggregate. It is concluded that the tegminal wing cells function exclusively as amplifiers. The vein network is suggested as a structural source of the aggregate. A cantilever model is used to represent probable vein oscillation.

Frequency spectra of some normal heart sounds

An experimental method has been described for obtaining the frequency spectra of heart sounds. Analyzed results are shown for some normal heart sounds. No attempt is made to correlate frequency peaks with specific sound sources since insufficient data is available and the mechanisms are imperfectly understood. A detailed frequency spectrum could conceivably be a valuable diagnostic tool if the various sound components could be related to specific cardiovascular mechanisms.