Tone Prominence Research Articles

On the impact of operating condition and testing environment on the noise sources in an industrial engine cooling fan

Engine cooling fan noise is a relevant issue for manufacturers. It is well known that both the operating point and testing environment can affect the noise generation mechanisms and, consequently, the measured noise may change. Therefore, these aspects are investigated on a reference industrial fan, for which experimental data exists, using high-fidelity numerical simulations based on the lattice-Boltzmann method. Two operating conditions, namely the free blowing and the maximum efficiency ones, and three testing environments are analyzed: (i) a conventional semi-anechoic room, (ii) an ideal free field environment, and (iii) a testing environment resembling an anechoic aeraulic facility. For cases (i) and (ii) no pressure difference across the fan is imposed, while, for case (iii), a pressure difference across the fan can be imposed. For the latter, the impact of a fully reflective and fully absorbing wall separating the two regions upstream and downstream of the fan is analyzed. At free blowing conditions, the flow over the blades is largely separated. When the blade passes through a blockage region, because of the presence of a honeycomb-like structure needed for structural purposes, it experiences a prominent loading hump. The far-field noise, at a listener located along the axis of rotation, is therefore highly tonal, with a clear peak at the blade passing frequency tone. When the same fan is tested in a free field environment, it is found that there is a difference in the acoustic pressure at higher harmonics of the blade passing frequency due to the presence of flow recirculations in the anechoic room. Placing a thin wall across the fan increases the mass flow rate, for a given rotational speed, which results in a more severe flow separation over the blades and, therefore a higher tone prominence at the blade passing frequency. If the thin wall is modeled as a sound-absorbing wall, there is a drop of the overall sound pressure level of about 2 dBA. When the fan is tested at its maximum efficiency, i.e., nonzero pressure difference across the fan, it is found that the blockage effect is less relevant. The main noise generation mechanism is the back-flow vortex induced by the pressure difference across the fan interacting with the blade tip leading edge.

The use of an artificial neural network for assessing tone perception in electric powertrain noise, vibration and harshness

The transition from internal combustion engines to electric powertrains brings new challenges for the Noise, Vibration, and Harshness (NVH) analysis of these vehicles. The tonal nature of the electromagnetic excitations and of the gear meshing mechanism are reflected in the radiated noise of electric powertrains, often leading drivers and passengers to rate the noise from electric vehicles with an increased nuisance even if they are quieter than internal combustion driven powertrains. In this paper, a flexible multi-body dynamics model is developed to calculate the vibration and forces transmitted from the bearings to the housing of an electric powertrain. Acceleration, force and sound spectra data are used to train an artificial neural network to assess the prominence of tones in the noise based on the results of the structural simulation. The results show it is possible to identify psychoacoustic metrics from the multibody dynamics simulation alone. With this new approach, it is feasible to quickly investigate how changes in the powertrain will affect the tonal perception of the noise without the need of new acoustic simulations and experiments. For the tonal perception analysis, the Prominence Ratio is used as a metric. This framework of combining multibody dynamics simulation with initial acoustic data and neural networks can be also applied to different NVH metrics as appropriate.

Rhythmical Features of Spontaneous Spoken Narrative in Mandarin Chinese

Every oral communication is shaped by a series of closely linked factors and rhythm is one of them. The rhythmical flow in colloquial Mandarin Chinese was thoroughly described by the Czech phonetician Oldřich Švarný, who invented a unique notation system dedicated to facilitating the teaching of Chinese as a foreign language. His prosodic transcription parses speech into a two-level arrangement of prosodic units. It displays the speech rhythm as an alternation of rhythmically significant and insignificant syllables of unequal tone prominence. The paper contributes to Švarný’s findings by shifting the attention from prefabricated teaching materials to an example of unrehearsed dynamic speech. Specifically, it attempts to outline the basic rhythmical features of personal narrative and confront them with the current understanding of speech rhythm in colloquial Chinese. It also demonstrates how Švarný’s methodological framework can be exploited to investigate different types of spoken discourse.

An air handling equipment manufacturer’s perspective on tonal noise measurement and application

In order to reliably predict sound from HVAC equipment, including tonal noise, sound power data needs to be determined for each noise producing component in the equipment. Though there are accepted standards for determining broad band sound in resolutions no finer than one-third octaves, there is a general lack of component data regarding tonal characteristics. This noise produced by the HVAC system in indoor environments is often an important source of masking noise improving speech privacy and the overall acoustical environment. The presence of prominent tones that are propagated into the space is counter to creating comfortable acoustical environments. The primary HVAC noise source is the fan and all fans produce tones at the blade pass frequency and harmonics. There is currently no accepted standard method of test for the tonality of fan noise. This paper proposes a standard method that can consistently be used to determine the tonality of fan noise, which can in turn be used to determine if when combined with other self gen noise generated by the air distribution system to determine the prominence of tones that will propagate to the occupied space.

Evaluation of tone annoyance metrics on reverberation room measurements of HVAC equipment

Reverberation rooms are a primary tool for HVAC equipment manufacturers to calculate equipment sound power levels, which lead directly to equipment sound ratings. While sound quality has been included in standards, namely, the withdrawn AHRI 1140, the adoption and value of those standards has been minimal leaving specifiers to construct their own tone quality metrics. This paper will evaluate the application of common sound quality metrics, specifically tonal metrics, to reverberation room measurements. Room response is a critical factor in measuring tone prominence, especially at lower frequencies where adjacent frequency tones can vary by 6dB or more. Metrics evaluated include TTNR, Prominence, Tonality and a new metric developed in ASHRAE 1707-TRP.

Acoustic measurement practices for UAS and UAM

Characterization of noise emission from novel aircraft types such as UAS and UAM is important for assessment of their impact on community soundscapes. Critical planning decisions such as the required buffer area between vertiports and noise-sensitive land uses will be made based on levels of interference with human activity. Traditional methods developed for fixed wing aircraft and helicopters may not be sufficient, because the sound character of UAS/UAM can make them more or less audible than their traditionally measured noise magnitude would suggest. Techniques have been developed that enable assessment of steady and time-varying loudness, tone prominence, sound quality and other metrics by adopting consistent calibrated procedures for acoustic waveform capture along with relevant metadata. This presentation will explore field procedures and data reduction employed to facilitate reconstruction of the aircraft sound at any receiver point on the ground, and subsequent application of existing or new metrics to this data.

On the position of topics in Japanese

Contrastive topics and non-contrastive topics in Japanese generally receive separate treatments in the literature: although they are both marked by the particle wa , the former carry tone prominence and only optionally move to clause-initial position, while the latter (Kuno's [1973] ‘theme’) do not carry tone prominence and typically occupy clause-initial position. This paper presents arguments that contrary to this standard view, topics in Japanese, contrastive or non-contrastive, must occupy clause-initial position. Evidence comes from examining the syntactic and interpretive properties of both types of wa- marked phrases in various discourse contexts. First, a tonally prominent wa -phrase must move to clause-initial position in contexts that require a contrastive topic. Second, in contexts that allow a tonally prominent wa -phrase to remain in situ, the relevant phrase is not interpreted as a topic and cannot move to clause-initial position. Third, tonally prominent wa- phrases displaced to clause-initial position show the syntactic distribution of topics that are predicted by considerations at the syntax-information structure interface, but those in situ do not. Finally, despite the general consensus, there are limited circumstances in which tonally non-prominent wa -phrases can occupy a non-initial position. The article presents syntactic and interpretive evidence that such wa- phrases are also not topics.

Implications of human performance and perception under tonal noise conditions on indoor noise criteria

This research investigated differences in task performance and perception under six non-time-varying ventilation-type background noise spectra with differing tonality. The results were related to five indoor noise criteria systems: noise criteria, balanced noise criteria, room criteria, room criteria mark II, and the A-weighted equivalent sound pressure level (L(Aeq)). These criteria systems are commonly used in the U.S. building industry, but concerns exist over whether they are appropriate for all noise situations. Thirty test subjects completed three types of performance tasks (typing, reasoning, and math) and answered questions about their perception of the indoor environment under each noise condition. Results showed that performance scores did not change significantly across the six noise conditions, but there were differences in subjective perception. For example, perception trends for tonality, annoyance, and distraction changed based on the frequency and prominence of discrete tones in noise. However, these perceptual changes were not fully reflected in the criteria level or spectral quality ratings. Additionally, task performance was related to subjective perception but not to criteria level predictions. As a result, the authors suggest that the current criteria should be modified to account for the frequency and prominence of tones in background noise.

Investigation of ocean acoustics using autonomous instrumentation to quantify the water-sediment boundary properties

Several noise criteria methods commonly used in architectural acoustics have been quantitatively related to noise perception and task performance under a variety of ventilation systems-induced background noise conditions. Noise criteria, balanced noise criteria, room criteria, room criteria mark II, and A-weighted equivalent sound pressure level were examined. The first phase of the project included noise conditions controlled to be non-time-varying and nontonal, with neutral, rumbly, roaring, or hissy characteristics. An intermediate study examined exposure time length and types of performance tasks used. The final phase included noise conditions containing various levels of discrete tones from 120 to 595 Hz. Under each noise, subjects completed performance tasks and perception questionnaires. Results indicate task performance was significantly affected by perception of noise, but this relationship was not fully demonstrated by the criteria systems analyzed. The five criteria were generally well suited in describing subjective loudness perception, but some discrepancies in criteria spectral quality ratings and subjective perception existed. Finally, perception of annoyance changed based on the frequency and prominence of tones in noise, but these changes were not reflected in the criteria level or spectral quality ratings. Modifications to the existing criteria are recommended.

Analysis of parameter effects on sound energy decay in coupled volume systems

Several noise criteria methods commonly used in architectural acoustics have been quantitatively related to noise perception and task performance under a variety of ventilation systems-induced background noise conditions. Noise criteria, balanced noise criteria, room criteria, room criteria mark II, and A-weighted equivalent sound pressure level were examined. The first phase of the project included noise conditions controlled to be non-time-varying and nontonal, with neutral, rumbly, roaring, or hissy characteristics. An intermediate study examined exposure time length and types of performance tasks used. The final phase included noise conditions containing various levels of discrete tones from 120 to 595 Hz. Under each noise, subjects completed performance tasks and perception questionnaires. Results indicate task performance was significantly affected by perception of noise, but this relationship was not fully demonstrated by the criteria systems analyzed. The five criteria were generally well suited in describing subjective loudness perception, but some discrepancies in criteria spectral quality ratings and subjective perception existed. Finally, perception of annoyance changed based on the frequency and prominence of tones in noise, but these changes were not reflected in the criteria level or spectral quality ratings. Modifications to the existing criteria are recommended.

Investigations of indoor noise criteria systems based on human perception and task performance

Several noise criteria methods commonly used in architectural acoustics have been quantitatively related to noise perception and task performance under a variety of ventilation systems-induced background noise conditions. Noise criteria, balanced noise criteria, room criteria, room criteria mark II, and A-weighted equivalent sound pressure level were examined. The first phase of the project included noise conditions controlled to be non-time-varying and nontonal, with neutral, rumbly, roaring, or hissy characteristics. An intermediate study examined exposure time length and types of performance tasks used. The final phase included noise conditions containing various levels of discrete tones from 120 to 595 Hz. Under each noise, subjects completed performance tasks and perception questionnaires. Results indicate task performance was significantly affected by perception of noise, but this relationship was not fully demonstrated by the criteria systems analyzed. The five criteria were generally well suited in describing subjective loudness perception, but some discrepancies in criteria spectral quality ratings and subjective perception existed. Finally, perception of annoyance changed based on the frequency and prominence of tones in noise, but these changes were not reflected in the criteria level or spectral quality ratings. Modifications to the existing criteria are recommended.

Tone prominence ratio, error sources, and proposed solutions

Tone prominence ratio is finding increasing use as a tool for product sound design. ECMA-74 Annex D offers a procedure for calculating tone prominence ratio and qualifying tone audibility. However, there are significant potential sources of error when utilizing the ECMA-74 procedure. These include possible misidentification of tone frequency, and ambiguities about what constitutes tone audibility. Misidentification of tone frequency can occur when closely spaced tones exist in the spectrum; whereas, other errors may result from individual subjective assessment of tone audibility. The existing ECMA method does not specify how to identify the primary tone frequency when such ambiguities exist. Real-world examples of potential error sources are presented along with proposed solutions. An unambiguous peak prominence ratio value reporting system is presented along with data to support its improved relevance in terms of hearing perception and subjective annoyance.

Computer sound quality: Masking, loudness and prominence

Computers and business equipment were one of the first applications for standardized sound quality metrics. Various product specifications (emanating primarily from Europe) defined criteria for A-weighted sound pressure and sound power levels as well as the absence of prominent tones and impulsive noise. Standards such as ISO 7779, ANSI S12.10 and ECMA 74 have provided the means for assessing these quantities. Of particular interest at the moment is the prominent tone, for which there are two accepted metrics: tone-to-noise ratio and prominence ratio. Experience has shown that both metrics occasionally fail to track listeners perception of the prominence of tones or tonal complexes. An alternate prominence analysis is constructed based on psychoacoustical factors, using a method proposed by Zwicker for identifying the loudness of any sound masked by another. The accepted metrics are compared and contrasted with the masked loudness method using carefully selected test cases.

The Perception of Tone Hierarchies and Mirror Forms in Twelve-Tone Serial Music

Four experiments are reported in which the materials are derived from two 12-tone serial compositions (Schoenberg's Wind Quintet and String Quartet, No. 4). Two experiments use the probe tone method (Krumhansl & Shepard, 1979) to assess factors contributing to tone prominence in serial music. The contexts in Experiment 1 are musically neutral statements of the complete or incomplete tone rows; the contexts in Experiment 4 are excerpts from the two pieces. Two experiments use a classification task to evaluate whether the prime form of the row is perceived as similar to its mirror forms (inversion, retrograde, and retrograde inversion). The materials are neutral presentations of the forms (Experiment 2) or excerpts from the pieces (Experiment 3). Large individual differences are found. A subgroup of listeners, with more music training on average, show the following effects in the probe tone experiments: low ratings for tones sounded more recently in the contexts and high ratings for tones not yet sounded; low ratings for tones fitting with local tonal implications; similar patterns for the neutral contexts and the musical excerpts. The remaining listeners show the opposite effects. Classification accuracy of mirror forms is above chance and is higher for the neutral sequences than the musical excerpts; performance is correlated with music training. The experiments show that some, but not all, listeners can perceive invariant structures in serial music despite mirror transformations, octave transpositions of tones, and variations of rhythm and phrasing.