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PubMed2000

Extracting spectral envelopes: formant frequency matching between sounds on different and modulated fundamental frequencies.

The four experiments reported here measure listeners' accuracy and consistency in adjusting a formant frequency of one- or two-formant complex sounds to match the timbre of a target sound. By presenting the target and the adjustable sound on different fundamental frequencies, listeners are prevented from performing the task by comparing the absolute or relative levels of resolved spectral components. Experiment 1 uses two-formant vowellike sounds. When the two sounds have the same F0, the variability of matches (within-subject standard deviation) for either the first or the second formant is around 1%-3%, which is comparable to existing data on formant frequency discrimination thresholds. With a difference in F0, variability increases to around 8% for first-formant matches, but to only about 4% for second-formant matches. Experiment 2 uses sounds with a single formant at 1100 or 1200 Hz with both sounds on either low or high fundamental frequencies. The increase in variability produced by a difference in F0 is greater for high F0's (where the harmonics close to the formant peak are resolved) than it is for low F0's (where they are unresolved). Listeners also showed systematic errors in their mean matches to sounds with different high F0's. The direction of the systematic errors was towards the most intense harmonic. Experiments 3 and 4 showed that introduction of a vibratolike frequency modulation (FM) on F0 reduces the variability of matches, but does not reduce the systematic error. The experiments demonstrate, for the specific frequencies and FM used, that there is a perceptual cost to interpolating a spectral envelope across resolved harmonics.

Auditory Perception↗
PubMed1979

Dependence of acoustic attenuation of hearing protectors on incident sound level.

The relationship between incident sound level and acoustic attenuation for four types of earplug and four types of earmuff have been investigated using freshly prepared and instrumented cadaver ears. Pure tones and 1/3-octave bands of random noise in the frequency range 125-8000 Hz were employed as steady-state stimuli with sound pressure levels between 75 and 125 dB. Impulses with peak sound levels in the range 135-175 dB(P) were also presented. For the steady-state signals employed, the eight hearing protectors have been shown to have constant attenuation characteristics over the range of incident sound levels investigated. This was also the case for the six conventional protectors (with intentionally linear characteristics) for the impulse stimuli. The two intentionally amplitude-sensitive protectors provided attenuation which increased with incident sound level for impulse noises. Comparison of the protector attenuation-frequency characteristics determined for steady-state sounds shows good agreement with those obtained from subjective (threshold shift) national standard measurement procedures. It may be concluded, therefore, that the six conventional hearing protectors studied here have attenuation characteristics that are equal for incident sound levels at about 40 and 75 dB, and that they are constant for levels between 75 and 175 dB. Consequently, the results of national standard threshold-shift procedures, although measured at low sound levels, may be applied with confidence to occupations where hazardous high-level noises are present.

Acoustic Stimulation↗
PubMed1989

Early detection of pulmonary congestion and edema in dogs by using lung sounds.

Five mongrel dogs (2 interstitial and 3 alveolar edema) were studied. Lung mechanics were measured by recording the flow, volume, and esophageal pressure according to the standard technique. Edema was produced by infusion of Ringer lactate solution. Lung sounds were recorded on tape from the dependent part of the chest wall. Lung sound signals were high-pass filtered at 100 Hz and subjected to fast Fourier transform. Samples of lung sounds were analyzed before (control) and at 5, 10, 20, 30, and 40 min after the infusion. The mean, median, and mode frequencies of sound power spectra at the control time were, respectively, 169.6 +/- 29.19, 129.6 +/- 29.81, and 136.0 +/- 29.87 (SD) Hz. These values increased significantly at 5 min after infusion to 194.0 +/- 26.08 (P less than 0.0037), 150.2 +/- 23.48 (P less than 0.0085), and 164.6 +/- 28.74 Hz (P less than 0.02), respectively. These values stayed significantly elevated at 10, 20, 30, and 40 min. The pulmonary wedge pressure, lung dynamic compliance, and pulmonary resistance were measured also at the same times. The mean, median, and mode frequencies correlated with pulmonary wedge pressure (P less than 0.00001, P less than 0.0001, P less than 0.0001), lung dynamic compliance (P less than 0.001, P less than 0.0001, P less than 0.0001), and pulmonary resistance (P less than 0.00001, P less than 0.00001, P less than 0.0001), respectively. There were no significant adventitious sounds up to 40 and 50 min after infusion. We concluded that pulmonary congestion and early edema alter the frequency characteristics of lung sounds early, before the occurrence of adventitious sounds. These altered lung sounds may be used as an index of pulmonary congestion and impending edema.

Animals↗
PubMed1996

Airflow effects on amplitude and spectral content of normal breath sounds.

Even though it is well known that breath-sound amplitude (BSA) increases with airflow, the exact quantitative relationships and their distribution within the relevant frequency range have not yet been determined. To evaluate these relationships, the spectral content of tracheal and chest wall breath sounds was measured during breath hold, inspiration, and expiration in six normal men. Average spectra were measured at six flow rates from 0.5 to 3.0 l/s. The areas under the spectral curves of the breath sounds minus the corresponding areas under the breath-hold spectra (BSA) were found to have power relationships with flow (F), best modeled as BSA = k.F alpha, where k and alpha are constants. The overall mean +/- SD value of the power (alpha) was 1.66 +/- 0.35, significantly less than the previously reported second power. Isoflow inspiratory chest wall sound amplitudes were 1.99 +/- 0.70- to 2.43 +/- 0.65-fold larger than the amplitudes of the corresponding expiratory sounds, whereas tracheal sound amplitudes were not dependent on respiratory phase. Isoflow breath sounds from the left posterior base were 32% louder than those from the right lung base (P < 0.01). BSA-F relationships were not frequency dependent during expiration but were significantly stronger in higher than in lower frequencies during inspiration over both posterior bases. These data are compatible with sound generation by turbulent flow in a bifurcating network with 1) flow separation, 2) downstream movement of eddies, and 3) collision of fast-moving cores of the inflowing air with carinas, all occurring during inspiration but not during expiration.

Adult↗
PubMed2002

Transpulmonary speed of sound input into the supraclavicular space.

The transpulmonary speed of sound input at the mouth has been shown to vary with lung volume. To avoid the disadvantages that exist in certain clinical situations in inputting sound at the mouth, we input sound in the supraclavicular space of 21 healthy volunteers to determine whether similar information on the relationship of sound speed to lung volume could be obtained. We measured the transit time at multiple microphones placed over the chest wall using a 16-channel lung sound analyzer (Stethographics). There was a tight distribution of transit times in this population of subjects. At functional residual capacity, it was 9 +/- 1 (SD) ms at the apical sites and 13 +/- 1 ms at the lung bases. The sound speed at total lung capacity was 24 +/- 2 m/s and was 22 +/- 2 m/s at residual volume (P < 0.001). In all subjects, the speed of sound was faster at higher lung volume. This improved method of studying the mechanism of sound transmission in the lung may help in the development of noninvasive tools for diagnosis and monitoring of lung diseases.

Acoustic Stimulation↗
PubMed2002

Changes of AI receptive fields with sound density.

Primates engage in auditory behaviors under a broad range of signal-to-noise conditions. In this study, optimal linear receptive fields were measured in alert primate primary auditory cortex (A1) in response to stimuli that vary in spectrotemporal density. As density increased, A1 excitatory receptive fields systematically changed. Receptive field sensitivity, expressed as the expected change in firing rate after a tone pip onset, decreased by an order of magnitude. Spectral selectivity more than doubled. Inhibitory subfields, which were rarely recorded at low sound densities, emerged at higher sound densities. The ratio of excitatory to inhibitory population strength changed from 14.4:1 to 1.4:1. At low sound densities, the sound associated with the evocation of an action potential from an A1 neuron was broad in spectrum and time. At high sound densities, a spike-evoking sound was more likely to be a spectral or temporal edge and was narrower in time and frequency range. Receptive fields were used to predict responses to a novel high-noise-density stimulus. The predictions were highly correlated with the actual responses to the 2-s complex sound excerpt. The structure of prediction failures revealed that neurons with prominent inhibitory fields had relatively poor linear predictions. Further, the finding that stochastic variance is limiting in prediction even after averaging 150 repetitions means that high-fidelity representations of simple sounds in A1 must be distributed over at least hundreds of neurons. Auditory context alters A1 responses across multiple parameter spaces; this presents a challenge for reconstructing neural codes.

Acoustic Stimulation↗
PubMed2004

Short-term sound temporal envelope characteristics determine multisecond time patterns of activity in human auditory cortex as shown by fMRI.

Functional magnetic resonance imaging (fMRI) of human auditory cortex has demonstrated a striking range of temporal waveshapes in responses to sound. Prolonged (30 s) low-rate (2/s) noise burst trains elicit "sustained" responses, whereas high-rate (35/s) trains elicit "phasic" responses with peaks just after train onset and offset. As a step toward understanding the significance of these responses for auditory processing, the present fMRI study sought to resolve exactly which features of sound determine cortical response waveshape. The results indicate that sound temporal envelope characteristics, but not sound level or bandwidth, strongly influence response waveshapes, and thus the underlying time patterns of neural activity. The results show that sensitivity to sound temporal envelope holds in both primary and nonprimary cortical areas, but nonprimary areas show more pronounced phasic responses for some types of stimuli (higher-rate trains, continuous noise), indicating more prominent neural activity at sound onset and offset. It has been hypothesized that the neural activity underlying the onset and offset peaks reflects the beginning and end of auditory perceptual events. The present data support this idea because sound temporal envelope, the sound characteristic that most strongly influences whether fMRI responses are phasic, also strongly influences whether successive stimuli (e.g., the bursts of a train) are perceptually grouped into a single auditory event. Thus fMRI waveshape may provide a window onto neural activity patterns that reflect the segmentation of our auditory environment into distinct, meaningful events.

Acoustic Stimulation↗
PubMed1990

Single-unit selectivity to azimuthal direction and sound pressure level of noise bursts in cat high-frequency primary auditory cortex.

1. The azimuth and sound pressure level (SPL) selectivities of single-unit responses recorded in primary auditory cortex of barbiturate-anesthetized cats were studied by the use of broadband noise bursts delivered in the free field from a moveable loud-speaker. The experiments were carried out with cats located inside a quasianechoic sound-isolation chamber. We studied 71 units with relatively stable response properties. All units were located in the frequency representation between 5.8 and 31 kHz. The data obtained for each unit were displayed as an azimuth-level response area, a contour plot that displays the distribution of response magnitude as a joint function of SPL and azimuth at 0 degrees elevation. From these, azimuth and level functions were obtained to derive descriptors of azimuth and level selectivity. 2. Sensitivity to sound-source azimuth was assessed from the modulation of the average azimuth function (average of azimuth functions obtained to each SPL of noise that was presented) for each unit. The sample was arbitrarily divided into a high-directionality (HD) group (66%) whose average azimuth functions had modulation values of greater than or equal to 75% and a low-directionality (LD) group (34%). The distinction between HD and LD groups was made so that we could analyze the characteristics of units likely to be involved in the representation of sound-source azimuth. 3. There is an overrepresentation of the contralateral sound field and the midline in the sample of HD units. The preferred sector for each unit was defined as the range of azimuths within the frontal sound field throughout which unit response was greater than or equal to 75% of maximum. Each unit was classified as either midline preferring (17%, the midpoint of the preferred sector, i.e., best azimuth, was located within 5 degrees of the midline), contralateral preferring (60%), or ipsilateral preferring (23%). The ratio of contralateral- to ipsilateral-preferring units was 2.5:1. A higher proportion of units had best azimuths located in the 10 degrees sector centered on the midline than in any other 10 degrees sector of the frontal sound field. 4. In one animal, recordings were obtained at seven closely spaced sites in layer IV from single- and multiunit responses, which were narrowly tuned to both azimuth and SPL. The units located along a 1-mm length of an isofrequency strip were tuned to similar frequencies and SPLs but had five distinctly different directional preferences distributed throughout the entire frontal sound field.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustics↗
PubMed1992

Encoding of sound-source location and movement: activity of single neurons and interactions between adjacent neurons in the monkey auditory cortex.

1. Neuronal mechanisms for decoding sound azimuth and angular movement were studied by recordings of several single units in parallel in the core areas of the auditory cortex of the macaque monkey. The activity of 180 units was recorded during the presentation of moving and static sound stimuli. Both the activity of single units and the interactions between neighboring neurons in response to each stimulus were analyzed. 2. Sixty-two percent of the units showed significant modulation of their firing rates as a function of the stimulus azimuth. Contralateral stimuli were preferred by the majority (approximately 60%) of these neurons. Thirty-five percent of the units showed mild but statistically significant modulation of their firing rates, which was specifically attributed to the angular movement of the sound source. 3. Eighty-nine percent of the "movement-sensitive" units were also "azimuth sensitive." The sound source's azimuth determined the pattern of the response components (on, sustained, off), whereas the source's movement affected only the magnitude of these components, typically the sustained component. Most neurons for which the sustained response to static sounds was greater for contralateral than ipsilateral stimuli preferred moving sounds that were moving into the contralateral hemifield. 4. Cross-correlation analysis was carried out for 245 neuron pairs. Cross-correlograms were computed for each pair under all stimulus conditions to allow comparison of the neuronal interactions under the various conditions. The shapes of some correlograms (after subtraction of direct stimulus effects) were dependent on specific stimulus conditions, suggesting that the effective connectivity between these neurons depended on the location and/or movement of the sound stimuli. Furthermore, joint peristimulus time (JPST) analysis indicated that modifications of connectivity may be temporally related to the stimulus and may occur over short periods of time. These results could not have been predicted from analysis of the independent single-unit responses to the stimuli. 5. The data suggest that both firing rates and correlated activity between adjacent neurons in the auditory cortex encode sound location and movement.

Acoustic Stimulation↗
PubMed1994

Sound localization after unilateral lesions of inferior colliculus in the ferret (Mustela putorius).

1. The ability of ferrets to localize sounds in space was determined before and after large unilateral lesions of the inferior colliculus. Three animals sustained restricted lesions that destroyed the inferior colliculus caudally but spared some tissue rostrally. These restricted lesions did not extend substantially beyond the cytoarchitectonic boundaries of the inferior colliculus. Four animals received more extensive lesions that destroyed all of the inferior colliculus, including the rostral pole. These lesions also involved to various degrees other midbrain structures, including the dorsal nucleus of the lateral lemniscus and the lateral tegmentum. Psychophysical curves and minimum audible angles were obtained for midline and left and right lateral fields. Comparisons were made of deficits ipsilateral and contralateral to the lesion. 2. The animals were tested in a semicircular apparatus with loudspeakers located at various positions around the periphery. Separate sound localization tests were conducted for midline, left, and right field positions. In each test the animals were trained first to discriminate between speakers separated by 60 degrees. They were then tested with progressively smaller angles of speaker separation to obtain their psychophysical threshold (minimum audible angle). All critical tests of sound localization were based on the ability of animals to identify the location of a 45-ms noise burst presented at the beginning of each trial. Correct responses were rewarded by delivery of a small quantity of water from spouts located around the perimeter of the apparatus. 3. Unilateral lesions restricted to the inferior colliculus had relatively little effect on sound localization. All three animals with restricted lesions were still capable of localizing a single noise burst and minimum audible angles were similar before and after surgery for midline, left, and right field tests. There was no difference in postoperative performance ipsilateral and contralateral to the lesion site. 4. More extensive unilateral lesions that included the dorsal nucleus of the lateral lemniscus and the lateral tegmentum as well as the inferior colliculus resulted in severe deficits in sound localization. Each of the four animals with large unilateral lesions had a substantial impairment in sound localization in the field contralateral to the lesion site. Postoperative performance in the contralateral field was too low to obtain a minimum audible angle for these animals. Midline sound localization was also affected in some cases but ipsilateral sound localization was only slightly affected.

Animals↗
PubMed1996

Effect of gas density on respiratory sounds.

The generation of normal lung sounds by turbulent air flow has been questioned because gas density appears to have only a minor effect. We studied whether gas density has a greater influence on lung sounds at higher frequencies than traditionally measured. Six healthy adult men breathed air followed by a mixture of 80% helium and 20% oxygen (He-O2) at a target flow of 1.5 L/s. Flow and sounds at the trachea and posterior right lower lobe were simultaneously acquired by computer. Fourier analysis was applied to sounds at target flow +/- 0.2 L/s. Average power spectra were computed for each recording site, respiratory phase, and respired gas. He-O2 reduced the power of inspiratory lung sounds below 300 Hz by only 1.7 +/- 1.5 dB whereas power between 300 and 600 Hz was reduced by 4.6 +/- 1.4 dB (p<0.05). Tracheal sound power was reduced less consistently but all subjects showed an upward frequency shift in power maxima on He-O2, similar to formant shifts observed in helium speech. Our findings suggest that flow turbulence is the major determinant of lung sounds at higher frequencies. Current instruments for auscultation and recording of respiratory sounds may have to be modified to optimize their response in this higher frequency range.

Adult↗
PubMed1983

Does the vesicular lung sound come only from the lungs?

Considerable confusion exists regarding the frequency spectrum of the normal lung sound, especially the components in the lower frequency range. Frequencies of peak intensity varying from 10 to 200 Hz have been reported by different laboratories. A component of musculoskeletal sound could contribute to the inspiratory lung sound, but this has never been assessed. This study attempted to separate the sound made by the lung from that of muscular contraction by frequency analysis of the sounds occurring during inspiration and preinspiration and postinspiration open-glottis breath-holds in 4 normal subjects. The data showed that at frequencies below 200 Hz, the musculoskeletal component increased as the lung sound component decreased. At 50 Hz and below, the sounds of inspiration and postinspiratory breath-holding were almost indistinguishable. It is concluded that musculoskeletal noise seriously contaminates what is usually considered to be lung sound.

Adult↗
PubMed2000

Lung sounds in asbestos induced pulmonary disorders.

The aim of the study was to compare the lung sounds in patients with asbestos related pulmonary disorders with findings in high-resolution computed tomography (HRCT), and with lung function variables, in order to find out associations of acoustic changes with radiological fibrosis, emphysema or with pulmonary gas transfer functions. Sixty-four patients with asbestos-related pleural disease, with or without pulmonary disease, were studied. Lung sound recording and analysis was carried out with a computerized lung sound analyser, and HRCT of the chest, as well as forced spirometry and diffusing capacity measurement were performed. The fibrosis score correlated positively with the quartile frequencies of the power spectrum of lung sounds in inspiration (f50) and expiration (f50) and crackle count in inspiration, as well as negatively with diffusing capacity. When the patients with crackling sounds and significant fibrosis were excluded (n=18), emphysema correlated negatively with expiratory quartile frequencies of the power spectrum, with f25 and f50. Furthermore, diffusing capacity correlated with inspiratory f25 and forced expiratory volume in one second with inspiratory f50 when crackles and fibrosis were excluded. Changes in lung sounds were significantly associated with radiologically verified abnormalities and gas transfer of pulmonary tissue. High sound frequencies were associated with fibrotic changes of the lung while low sound frequencies with pulmonary emphysema. Acoustic analysis gives complementary clinical information for evaluation of asbestos-related pulmonary disorders.

Aged↗
PubMed1994

Respiratory health screening using pulmonary function tests and lung sound analysis.

Lung sounds (LS) analysis is a potential source of additional objective, noninvasive and quantitative information on the status of the pulmonary system. We have examined the hypothesis that the addition of lung sounds analysis to spirometry increases the sensitivity of objective population screening, as compared to the use of spirometry alone. Questionnaires, spirometry and lung sounds were obtained in 493 active workers. Lung sounds analysis consisted of the averaged power spectra of breath sounds, measured separately during inspiration and expiration at four standard locations over the trachea and the chest-wall. Of the 493 subjects, 91 had an obstructive lung disease, including 27 with chronic bronchitis identified by a history of prolonged cough and sputum production but with normal spirometry. Twelve additional workers had a restrictive lung disease. Abnormal spirometric results were found in 74 of the patients. Abnormal lung sounds analyses were found in 54 patients, including 14 of the chronic bronchitis cases, so that the overall sensitivity of objective screening tests increased from 71% to 87% by combining the two tests. Thirty three of the subjects considered normal by evaluation of their questionnaire and spirometry had abnormal lung sounds. Of the twenty four who were re-evaluated 12-18 months after the first tests, three had developed a lung or heart disease. We conclude that the combination of spirometry and lung sounds analysis significantly increased the sensitivity of detection of pulmonary diseases by objective tests, and provided an early sign of lung disease that was not detected by spirometry alone.

Adult↗
PubMed1984

Frequency analysis of the first and second heart sounds of humans.

Each sound signal of the first and the second heart sounds of humans was divided into three equal segments. The frequency spectrum of each segment was analyzed using the fast-Fourier-transform technique. Theory predicts that if the first and second heart sounds are caused principally by the respective vibrations of the atrioventricular and semilunar valves, then the frequency of these sounds should increase with an increase in the pressure difference across these valves. In other words, the frequency of the heart sounds should increase with time, as the pressure difference across these valves increases with time for most of the duration of the sounds. Our frequency analysis, however, showed that there is no systematic relation between the predominant frequency of successive segments of the sound signals. This therefore appears to indicate that it is quite unlikely that the vibrations of the heart valves are the principal contributor to the origin of the first and second heart sounds.

Adult↗
PubMed1999

Analysis of gastrointestinal sounds in infants with pyloric stenosis before and after pyloromyotomy.

BACKGROUND: Although recent advances in computer technology enable us to analyze gastrointestinal sounds data objectively with ease, this clinical application has been investigated in only a few disorders. To investigate one potential role of this approach in pediatric practice, we recorded and analyzed gastrointestinal sounds in infants with hypertrophic pyloric stenosis (HPS), a motility-related disorder that is common in children. METHODS: In 15 infants with pyloric stenosis, gastrointestinal sounds were collected with a microphone placed 3 cm below the umbilicus for 60 minutes before pyloromyotomy and at 9 to 12 hours, 20 to 24 hours, 40 to 48 hours, and 112 to 120 hours after the operation. Data were entered into a computer to sum the amplitude of sound signals as a sound index (SI; mV per minute). In 12 infants, gastric emptying was measured immediately before each sound recording, using a marker dilution-double sampling method. RESULTS: Before surgery, the mean SI was 4.6 +/- 1.0 mV per minute, significantly less than in healthy controls (31.7 +/- 8.4 mV per minute). The SI remained in a similar range until 12 hours after operation, after which it began increasing to reach the normal range by 48 hours after operation (30. 0 +/- 9.4 mV per minute). Gastric emptying, also low in HPS before pyloromyotomy, increased by 4 to 5 times after surgery. There was a significant positive correlation between SI and gastric emptying. The incidence of postoperative symptoms (such as vomiting) were correlated significantly with SI at 24 hours after surgery. CONCLUSION: This study found decreased gastrointestinal sounds to be among physical findings suggestive of HPS and a useful indicator of gastric emptying and bowel motility after pyloromyotomy. Computer-assisted analysis of gastrointestinal sounds might be helpful in clinical practice for pediatric patients with some gastrointestinal disorders.

Analysis of Variance↗
PubMedDate not supplied

Sound level exposure of high-risk infants in different environmental conditions.

PURPOSES: To provide descriptive information about the sound levels to which high-risk infants are exposed in various actual environmental conditions in the NICU, including the impact of physical renovation on sound levels, and to assess the contributions of various types of equipment, alarms, and activities to sound levels in simulated conditions in the NICU. DESIGN: Descriptive and comparative design. SAMPLE: Convenience sample of 134 infants at a southeastern quarternary children's hospital. MAIN OUTCOME VARIABLE: A-weighted decibel (dBA) sound levels under various actual and simulated environmental conditions. RESULTS: The renovated NICU was, on average, 4-6 dBA quieter across all environmental conditions than a comparable nonrenovated room, representing a significant sound level reduction. Sound levels remained above consensus recommendations despite physical redesign and staff training. Respiratory therapy equipment, alarms, staff talking, and infant fussiness contributed to higher sound levels. CONCLUSION: Evidence-based sound-reducing strategies are proposed. Findings were used to plan environment management as part of a developmental, family-centered care, performance improvement program and in new NICU planning.

Child Development↗
PubMed2004

Evaluation method of artificial acoustical environment: visualization of sound intensity.

Recent development of sound reproduction systems such as 5.1 surround produces artificial sound field inside the enclosure. The acoustic characteristic of the enclosure is an important factor which determines the quality of the sound field reproduction. This paper provides a useful method for evaluating the characteristics of the sound field in the enclosed space. The proposed method is based on the visualization of the measured sound intensity. In this research, the sound intensity is obtained by measuring the impulse responses from the sound source to the receiving points. The direction and the strength of the intensity can be interpreted as having a strong correlation with the reflected sound from the corresponding direction. The proposed method thus projects that information, i.e., the arriving direction and the strength of the intensity, as the circle having appropriate radius onto the surface of the rectangular wire-frame box. This visualization makes it easy to grasp the fundamental characteristics of the reflections in the enclosure.

Acoustics↗