Interaural Cross-correlation Function Research Articles

Delving into Hearing Threshold of the Delay Gap of Initial Reflection in a Room by Using the Response of Cortical Brainwaves

In this study, the apparent variation ranges of acoustical parameters were investigated in a concert hall. The initial time delay gap (ITDG) was evaluated in terms of its just noticeable difference (JND) through two instruments, the cello and the trumpet. Even though the IDTG values were prolonged over the measurements and were not significantly varied, an ITDG range of 22–220 ms in increments of 91 steps was produced electro-acoustically in an anechoic chamber. The result of JNDc (Δgap/gap) was rated by 50% “different” judgement ranges for the cello and trumpet tracks, respectively. The effective duration of the autocorrection function (ACF) of the continuous brainwaves (CBWs) within the alpha (8–13 Hz) frequency range in the left hemisphere responding to 91-step ITDG increments revealed that the continuous ratios of τe_min ((τe_min_rear − τe_min_front)/τe_min_front) of CBWs were constantly on the trumpet. Furthermore, a homologous period of resonance between the subjective JNDc and τe values of the ACF of CBWs in the alpha range allowed us to conclude that the subjective JND of the ITDG in a room was related to the W_IACC value of the interaural cross-correlation function, which reflected the characteristics of source signals themselves and aroused the activities of the brain in the right hemisphere (p < 0.01). The dry sources of sound stimuli were first used to link the psychological preference and the neurophysiological activation of the room acoustics.

Remote Binaural System (RBS) for Noise Acoustic Monitoring

The recent emergence of advanced information technologies such as cloud computing, artificial intelligence, and data science has improved and optimized various processes in acoustics with potential real-world applications. Noise monitoring tasks on large terrains can be captured using an array of sound level meters. However, current monitoring systems only rely on the knowledge of a singular measured value related to the acoustic energy of the captured signal, leaving aside spatial aspects that complement the perception of noise by the human being. This project presents a system that performs binaural measurements according to subjective human perception. The acoustic characterization in an anechoic chamber is presented, as well as acoustic indicators obtained in the field initially for a short period of time. The main contribution of this work is the construction of a binaural prototype that resembles the human head and which transmits and processes acoustical data on the cloud. The above allows noise level monitoring via binaural hearing rather than a singular capturing device. Likewise, it can be highlighted that the system allows for obtaining spatial acoustic indicators based on the interaural cross-correlation function (IACF), as well as detecting the location of the source on the azimuthal plane.

Effects of spatial characteristics of footsteps sounds and non-acoustic factors on annoyance in lightweight timber buildings

This study investigates the effect of spatial characteristics of footsteps sound from upstairs in wooden residential buildings together with the influence of non-acoustic factors on annoyance ratings. Footsteps sound were recorded in the laboratory, where a typical lightweight timber joists floor is located between the source and receiving room. Two adults walked on the floor over three different paths (figure-of-eight, straight, and walking on the spot) at two different paces (very slow and normal). The spatial features of the recordings were quantified in terms of the magnitude of interaural cross-correlation (IACC) function. A total of 46 participants were recruited and they assessed their subjective annoyance after exposure to noise under laboratory conditions. During the laboratory experiments, 360-degree pictures of a living room during daytime or night-time were presented via a Head-Mounted Display (HMD). In addition, the participants were asked to answer questions concerning noise sensitivity, chronotype, and attitude towards neighbours. Results highlighted that IACC had a significant effect on annoyance, showing an increase in annoyance with increasing IACC. Footsteps at a very slow pace were more annoying than those at a normal pace. It was also found that annoyance ratings with a presentation of the living room during daytime were greater than those with a presence of the night-time living room. Furthermore, noise sensitivity, circadian rhythm, and attitude towards neighbours of participants were significant in moderating annoyance ratings.

Binaural sound source localization based on weighted template matching

In robot binaural sound source localization (SSL), locating the direction of the sound source accurately in the shortest time is important. It refers to the algorithm complexity, but even more to the shortest duration of the required signal. A novel binaural SSL method based on feature and frequency weighting is proposed. More specifically, in the training stage, the direction-related interaural cross-correlation function(CCF) and interaural intensity difference(IID) in each frequency band are calculated under noiseless conditions, which are considered the templates. In the testing stage, first the cosine similarities between the CCF and IID of the test signal and templates are calculated in all features and frequency bands. Then, the direction likelihood can be obtained by weighting the similarities. Finally, the direction with maximum likelihood is specified as the direction of the sound source. Experiments were carried out on CIPIC dataset subject 003 with different noises in the noisex-92 dataset and demonstrated that the method can accurately locate the sound source with a short signal duration.

Binaural Capability of Locating Sound Sources of Information Signals

The purpose of the work done was to estimate the human binaural capability of locating stereo sound sources of information signals, especially speech, choir singing, and symphonic music as compared to pulse signals. The measurements were conducted in an average-sized hall where sound was emitted by a stereo system consisting of two loudspeakers with the base width of 4.5 m.Based on the results of analysis of existing methods of binaural sound perception modelling, the estimation was performed based on correlational processing of signals recorded using a head dummy placed in various points of the room.For the recording points selected, the maximum time delays between signals arriving at a listener’s left and right ears were calculated, and the interaural cross-correlation functions were obtained. The general functions, especially the peak shift, correlation interval, and peak sharpness (including the conditions when it splits into two individual ones), were analysed. The correlation factor values and levels were calculated. As a result, the conclusions regarding the capability of locating an imaginary sound source were made based on the cross-correlation function factors values, which simplified the application of this method in practice.Based on the results of experiments conducted and on the subjective sensations of perception, the authors have come to the conclusion that a stereophony area has sizes much wider than those assumed earlier from the signal time delay of 1 ms at a receiving stereo pair (representing a shift of an imaginary source towards the ear perceiving the signal earlier).At the same time, it was found that signals with a speech component are much harder to locate than pulse signals. While music signals, especially symphonic music, are close to pulse signals in terms of human locating capabilities.The found patterns have allowed us to introduce adjustments to the stereophony area calculations. Based on the research results, we suggest defining the stereophony zone border by the correlation factor value of 0.5. Given that, the interaural cross-correlation function properties and subjective perception provide for acceptable speech legibility and music transparency. The key conclusion is that this area is quite narrow for speech signals and is actually limited to the time delay of signals arriving at left and right ears – around 1 ms. Music signals have a wider stereophony area defined by the time delay between perception binaural pair components of around 10 ms. Therefore, sizes of a stereophonic sound area ought to be defined with regard to an information signal’s type.Ref. 14, fig. 3, tabl. 3.

Autocorrelation function mechanism for pitch salience and cross-correlation function mechanism for sound localization revealed by magnetoencephalography

A model of primary sensations and spatial sensations is proposed by Ando (2001). The model of the auditory-brain system includes the autocorrelation function (ACF) and the interaural cross-correlation function (IACF) mechanisms. At present, environmental noises are evaluated by sound level such as equivalent continuous A-weighted sound pressure level (LAeq). However, we sometimes feel annoyed with sound with low sound level because of the quality. Sound quality can be characterized by factors obtained from ACF and IACF of sound. For example, pitch and pitch strength can be characterized by delay time and amplitude of the maximum peak of the ACF. Directional sensation can be characterized by delay time and amplitude of the maximum peak of the IACF. To verify the model, we investigated how ACF and IACF factors are coded in our human brain. The results indicated that delay time and amplitude of the maximum peak of the ACF and IACF are coded by the latency and strength of brain activity. In addition, we applied the model to analyze a Buddhist sutra chanted in temples. The results indicated that some characteristics of the sutra could be characterized by the ACF and IACF factors.

Temporal and spatial characteristics of noise in train stations

The train noise in station (TNIS) can annoy passengers and reduce the speech intelligibility of the public address system in a station. Thus clarifying the acoustical characteristics of TNIS is important for the comfort and safety. Noise level was evaluated the equivalent continuous sound pressure level (LAeq). The sound diffuseness was evaluated by the interaural cross-correlation coefficient (IACC) from the interaural cross-correlation function. The pitch and pitch strength was evaluated by the delay time (t1) and amplitude (f1) of the first peak of the autocorrelation function. The LAeq and IACC of the TNIS in the underground station were higher and lower, respectively, than those in the ground station. The t1 and f1 of the TNIS in the underground station were stable and lower, respectively, than those in the ground station. When the train came into the station, the LAeq of the TNIS at the island platform were higher than that at the side platform. The result suggests that the underground island platform, which is one platform at the center and the rail tracks on the both sides, needs improvement in particular although it is most frequently adopted as newly constructed stations in Japan.

Change of acoustic characteristics caused by platform screen doors in train stations

Railway companies are encouraged to install platform screen doors (PSDs) for safety reason in Japan. The PSDs might affect train noises in stations, but the effects are not well understood. The aim of the present study is to clarify the effects of PSDs on acoustic characteristics. PSDs can be principally classified by two types, i.e., mobile full-height (MFH) and mobile half-height (MHH). Train noises were recorded in ground and underground train stations with MFH, MHH and without PSDs. The noises were evaluated by noise level, the maximum peak of the interaural cross-correlation function (IACC), and the width of the first decay (WΦ(0)) of the autocorrelation function. Noise level emitted by trains was reduced by PSDs in both aboveground and underground stations. IACC was decreased by PSDs in both ground and underground stations, suggesting that PSDs made train noises more diffused. WΦ(0) was decreased by PSDs in both ground and underground stations, which means that the train noises in station with PSDs have higher spectral centroid, suggesting that the PSDs blocked the lower frequency components of train noises.

Relationships between interaural cross-correlation function and spatial impression of sound reproduced with five loudspeakers

Relationships between interaural cross-correlation function and spatial impression of sound reproduced with five loudspeakers

La miliaire tuberculeuse : à propos de 20 cas

Railway companies are encouraged to install platform screen doors (PSDs) for safety reason in Japan. The PSDs might affect train noises in stations, but the effects are not well understood. The aim of the present study is to clarify the effects of PSDs on acoustic characteristics. PSDs can be principally classified by two types, i.e., mobile full-height (MFH) and mobile half-height (MHH). Train noises were recorded in ground and underground train stations with MFH, MHH and without PSDs. The noises were evaluated by noise level, the maximum peak of the interaural cross-correlation function (IACC), and the width of the first decay (WΦ(0)) of the autocorrelation function. Noise level emitted by trains was reduced by PSDs in both aboveground and underground stations. IACC was decreased by PSDs in both ground and underground stations, suggesting that PSDs made train noises more diffused. WΦ(0) was decreased by PSDs in both ground and underground stations, which means that the train noises in station with PSDs have higher spectral centroid, suggesting that the PSDs blocked the lower frequency components of train noises.

Characteristics of train noise in above-ground and underground stations with side and island platforms

Railway stations can be principally classified by their locations, i.e., above-ground or underground stations, and by their platform styles, i.e., side or island platforms. However, the effect of the architectural elements on the train noise in stations is not well understood. The aim of the present study is to determine the different acoustical characteristics of the train noise for each station style. The train noise was evaluated by (1) the A-weighted equivalent continuous sound pressure level ( L Aeq), (2) the amplitude of the maximum peak of the interaural cross-correlation function (IACC), (3) the delay time ( τ 1) and amplitude ( ϕ 1) of the first maximum peak of the autocorrelation function. The IACC, τ 1 and ϕ 1 are related to the subjective diffuseness, pitch and pitch strength, respectively. Regarding the locations, the L Aeq in the underground stations was 6.4 dB higher than that in the above-ground stations, and the pitch in the underground stations was higher and stronger. Regarding the platform styles, the L Aeq on the side platforms was 3.3 dB higher than on the island platforms of the above-ground stations. For the underground stations, the L Aeq on the island platforms was 3.3 dB higher than that on the side platforms when a train entered the station. The IACC on the island platforms of the above-ground stations was higher than that in the other stations.

An investigation of floor impact sources and perception models of impact sounds

The present work compared the physical and psychoacoustical characteristics of standard impact sources with those of human impacts, and proposed the perception models of annoyance for impact sounds with respect to temporal and spatial aspects. Impact ball (heavy/soft impact source) was selected as an appropriate standard floor impact source simulating real floor impacts based on the objective evaluation and similarity judgment. Then, measurements using impact ball were conducted in a variety of apartment buildings with different floor structure and coverings. Variations in frequency characteristics were found in the measurement results, thus these were classified into three groups, Groups A-C. Differences between Groups A-C were clarified using sound quality metrics. Finally, perception models of impact ball sounds were developed in relation to temporal aspects and spatial characteristics, respectively. When the spatial characteristics kept constant, perceptions of annoyance for impact ball sounds were affected mainly by the differences in fluctuation strength as well as loudness. Another perception model comprised of IACC (Interaural cross-correlation function) was also proposed through auditory experiments. It was found that IACC had an effect on the perception of impact ball sounds with sound pressure level, and the contribution of IACC on perception of impact ball sounds was around 20%

Deconstructing the interaural cross-correlation function.

Because it is a measure of the similarity of signals in a listener’s left and right ears, the long-term interaural cross-correlation (IACC) function within one-third octave bands provides an estimate of auditory envelopment as well as a guide to the ability to localize a sound. The peak height of the IACC, known as the coherence, is particularly relevant. The IACC can be written mathematically in terms of the amplitudes of spectral components in the left and right ears and in terms of the interaural differences in the component phases. The ensemble-average IACC, as measured with an artificial head in real rooms, can be further analyzed in terms of the amplitudes—their statistical distributions and their interaural correlations—and in terms of the interaural phases—their distributions and correlations with amplitudes. The nature of these statistical relationships depends on the frequency range through the ratio of a characteristic wavelength to the head radius. Analysis of this kind helps solve the long-wavelength problem. In the long-wavelength limit, the IACC must be large, but that does not mean that sound localization is good. [Work supported by the NIDCD Grant DC00181.]

Subjective evaluation of heavy-weight floor impact sounds in relation to spatial characteristics

This study investigated the effect of a spatial factor, the magnitude of interaural cross-correlation (IACC) function, on subjective responses to heavy-weight floor impact sounds. Heavy-weight impact sounds were generated by a heavy/soft impact source (impact ball) in real apartments, so that impact sound pressure levels (SPLs) (L(Amax)) and IACC could be analyzed. Just noticeable differences (JNDs) of impact SPL and IACC were investigated through the use of impact ball sounds. JNDs were determined by the criteria of 75% correct answers by participants, and it was found that JNDs of impact SPL and IACC were around 1.5 dB and 0.12-0.13, respectively. In addition, the annoyance caused by an impact ball was evaluated by changes in these two parameters. The results show that annoyance increased with increasing impact SPL and with decreasing IACC; the contributions of the two parameters to the scale value of annoyance were 79.3% and 20.4%, respectively. This indicates that the effects of IACC should be considered for the evaluation of annoyance, and the subjective response to impact ball sounds can be improved by controlling IACC, as well as impact SPL.

The salience of interaural temporal disparities (ITDs) conveyed by high-frequency signals is determined by the temporal features of their ongoing envelopes

Many studies of binaural hearing reveal that envelopes of complex, high-frequency stimuli convey useful interaural time differences (ITDs). Envelope-based ITDs have, typically, been found to be less "potent" than those conveyed by low-frequency waveforms. When considering such findings, Blauert, in his classic textbook, noted that monaural, peripheral processing would result in 1) low-frequency inputs to the binaural processor that are essentially half-wave rectified versions of the input waveforms and 2) high-frequency inputs that are essentially full-wave rectified versions of only the envelopes of the input waveforms. Taking this into account, Blauert, echoing Colburn and Esquissaud (1976), surmised that low-frequency signals would ultimately convey "more distinct time cues" having greater "transient features" than would high-frequency signals and, therefore, be expected to provide more precise ITD information. By using high-frequency "transposed" stimuli having envelopes constructed to provide "more distinct time cues" we have shown in a variety of experimental contexts that the potency of envelope-based ITDs, can rival that measured with low-frequency stimuli. Our most recent experiments use "raised sine stimuli" in order to vary directly the temporal features of the envelope waveform including its "sharpness," "off-time," and interaural cross-correlation function. The new data will be discussed in terms of Blauert's insight.

Annoyance of noise stimuli in relation to the spatial factors extracted from the interaural cross-correlation function

While considering auditory–brain model for subjective responses, effects of spatial factors extracted from the interaural cross-correlation function (IACF) on annoyance of noise stimuli are examined. The previously developed indices to measure sound pressure levels (SPL) and frequency characteristics cannot fully explain the psychological effects of noise. In the first experiment, subjects judged their annoyance by changing fluctuations in the magnitude of interaural cross-correlation function (IACC) and the SPL. In the second, they judged their annoyance by changing fluctuations in the interaural time delay ( τ IACC ) and the SPL. Results show that: (1) annoyance increased by increasing the fluctuations of IACC as well as the SPL, (2) annoyance increased by increasing the fluctuations of τ IACC as well as the SPL.

Computer software for identification of noise source and automatic noise measurement

A new computational system for the environmental noise measurement and analysis has been developed. The system consists of binaural microphones, a laptop PC, and analysing software. A target noise is recorded automatically depending on the specified background noise level, and the acoustical parameters are calculated simultaneously. These functions allow for precise field measurements. The system is equipped with a template-matching algorithm for the identification of noise source. This function was implemented to avoid the effect of an interrupting sound such as voice and wind blowing during a measurement. Noise analyses in this system are based on the model of human auditory system. In addition to the time-series data of sound level, the important acoustical parameters of noise source are extracted from the running autocorrelation function (ACF) and the inter-aural cross-correlation function (IACF). It has been found that those parameters are strongly related to the auditory primary sensations and spatial sensations. Evaluation of the environmental noise based on these functions is another feature of this system. This paper describes the effectiveness of the ACF and the IACF analysis for analysing acoustical properties of noise and for evaluating the subjective response to noise.

Theory of acoustic design of opera house and a design proposal

First of all, the theory of subjective preference for sound fields based on the model of auditory-brain system is briefly mentioned. It consists of the temporal factors and spatial factors associated with the left and right cerebral hemispheres, respectively. The temporal criteria are the initial time delay gap between the direct sound and the first Reflection (Dt1) and the subsequent reverberation time (Tsub). These preferred conditions are related to the minimum value of effective duration of the running autocorrelation function of source signals (te)min. The spatial criteria are binaural listening level (LL) and the IACC, which may be extracted from the interaural crosscorrelation function. In the opera house, there are two different kind of sound sources, i.e., the vocal source of relatively short values of (te)min in the stage and the orchestra music of long values of (te)min in the pit. For these sources, a proposal is made here.

Method for evaluating sound and system for carrying out the same

A system and method (and storage media) for identifying the category of the source noise and sound by using the physical factors derived from the autocorrelation function (ACF) and the interaural crosscorrelation function (IACF) which are ever changing in the time domain based on the model of human auditory brain function system. A method for evaluating a sound comprises the steps of: using the sound recorder to capture and record the acoustic signal; calculating the ACF from the acoustic signal using a CPU; calculating ACF factors extracted from the calculated ACF using the CPU; and identifying the kinds of the noise based on the ACF factors. Thereby the unknown noise source can be identified what it is (such as automobile noise, and factory noise), and can be identified its type such as type of cars or type of machines.

On the temporal window of auditory-brain system in connection with subjective responses

The human auditory-brain system processes information extracted from autocorrelation function (ACF) of the source signal and interaural cross correlation function (IACF) of binaural sound signals which are associated with the left and right cerebral hemispheres, respectively. The purpose of this dissertation is to determine the desirable temporal window (2T: integration interval) for ACF and IACF mechanisms. For the ACF mechanism, the visual change of Φ(0), i.e., the power of ACF, was associated with the change of loudness, and it is shown that the recommended temporal window is given as about 30(τe)min [s]. The value of (τe)min is the minimum value of effective duration of the running ACF of the source signal. It is worth noticing from the experiment of EEG that the most preferred delay time of the first reflection sound is determined by the piece indicating (τe)min in the source signal. For the IACF mechanism, the temporal window is determined as below: The measured range of τIACC corresponding to subjective angle for the moving image sound depends on the temporal window. Here, the moving image was simulated by the use of two loudspeakers located at ±20° in the horizontal plane, reproducing amplitude modulated band-limited noise alternatively. It is found that the temporal window has a wide range of values from 0.03 to 1 [s] for the modulation frequency below 0.2 Hz. Thesis advisor: Yoichi Ando Copies of this thesis written in English can be obtained from Kiminori Mouri, 5-3-3-1110 Harayama-dai, Sakai city, Osaka 590-0132, Japan. E-mail address: km529756@aol.com