Acoustic Comfort Assessment Scale (ACAS-12)

Abstract

The Acoustic Comfort Assessment Scale (ACAS-12), developed by Herranz-Pascual et al. in 2023, is a comprehensive psychometric instrument designed to quantify the subjective pleasantness and quality of the acoustic environment within urban settings. Its theoretical foundation aligns with the principles established in the international standard ISO 12913–1:2014 (Acoustics—Soundscape). The ACAS-12 employs a 5-point semantic differential scale format, utilizing twelve pairs of bipolar adjectives that were initially organized across five theoretical dimensions. Data for its development were collected from urban open spaces in Spain. While initially conceptualized multi-dimensionally, subsequent Confirmatory Factor Analysis (CFA) strongly indicated that the most effective factorial solution is a single, robust factor encompassing all 12 adjective pairs. The scale has demonstrated high levels of reliability and validity for assessing human perception of urban soundscapes.

Keywords

Acoustic Comfort, Acoustic Environment, Human Perception Assessment, Noise, Acoustics, Auditory Perception, Noise Effects, Perceptual Measures, Physical Comfort, Urban Environments, Human Factors Measures.

Authors

Herranz-Pascual, Karmele, Iraurgi, Ioseba, Aspuru, Itziar, Garcia-Pérez, Igone, Eguiguren, José Luis, Santander, Álvaro.

Purpose

The primary purpose of the ACAS-12 is to serve as a specialized tool for assessing human perception of the acoustic environment, specifically targeting acoustic comfort in urban public spaces. It moves beyond objective decibel measurements to capture the subjective, qualitative experience of sound.

The instrument provides urban planners, acousticians, and researchers with a standardized, validated method to evaluate the success of soundscape interventions and to gauge the perceived quality of auditory environments in line with modern soundscape concepts.

Construct

The ACAS-12 measures the psychological construct of Acoustic Comfort. This construct is defined as the subjective level of pleasantness, suitability, and quality experienced by an individual concerning the surrounding acoustic environment.

Although the scale was initially designed to capture five distinct theoretical dimensions of acoustic perception, the final, empirically supported structure is unifactorial. This means the 12 bipolar adjective pairs function together to measure a single, overarching dimension of soundscape quality and comfort perception.

Validity

The scale provides strong evidence supporting its structural and construct validity. The rigorous procedures of factor analysis confirm that the ACAS-12 measures the intended construct effectively.

Specifically, the results of the Confirmatory Factor Analysis (CFA) indicated a robust fit for the single-factor model, confirming the structural validity necessary for a reliable assessment of acoustic comfort in urban contexts.

Reliability

The ACAS-12 demonstrates excellent internal consistency, ensuring that the items reliably measure the shared underlying construct.

This high level of reliability is statistically supported by a Cronbach’s alpha coefficient of 0.91. Furthermore, the composite reliability of the scale was reported at 0.90, reinforcing the measure’s stability and consistency.

Factor Analysis

The structural integrity of the ACAS-12 was primarily assessed through Confirmatory Factor Analysis (CFA). The analysis revealed that a unifactorial model, comprising all 12 pairs of adjectives, offered the most suitable fit. This single factor was estimated to explain approximately 50% of the total ACAS-12 variance (44% extracted variance using Raykov’s method or 56% via the MAP test).

The model fit indices met standard psychometric requirements. Both the absolute fit index and the Incremental Fit Index (IFI) were above the threshold of 0.90. Residual-based indices also indicated good fit (SRMR = 0.057; RMSEA = 0.042).

A modified 10-item version (ACAS-10) was also tested, which yielded slightly better fit indices (e.g., CFI = 0.99; RMSEA = 0.026). However, the developers opted to retain the 12-item version (ACAS-12) because the two items with lower contributions provided crucial information regarding acoustic comfort qualities, particularly the dimension of “Familiarity,” which is theoretically important in soundscape research.

Instrument

Test Type: Original

Format: Items are rated using a 5-point semantic differential scale, featuring twelve pairs of bipolar adjectives.

Language Available: English; Spanish. The English version was created using the rigorous back-translation technique.

Population Group: Human

Age Group: No data is Available

Population Details: Data was collected from respondents situated in urban open places and public spaces across Spain.

Test Methodology: The development and validation involved comprehensive psychometric methods, including Test Validity, Construct Validity, Test Reliability, Internal Consistency, Factor Analysis, and Confirmatory Factor Analysis (CFA).

Keywords

Acoustic Comfort, Soundscape Assessment, Auditory Perception, Psychometrics, Urban Planning, Environmental Psychology, Noise Effects, Semantic Differential.

Authors

Author ORCID Identifier: http://orcid.org/0000-0003-3930-5445 (Herranz-Pascual, Karmele)

Affiliation Email addresses: [email protected]

Correspondence Address: [email protected]

Permissions & Fee and Test Year

Permissions: The scale may be used freely for research and teaching purposes. The license governing its use is the Creative Commons Attribution 4.0 International License.

Fee: No fee is associated with the use of this scale.

Test Year: 2023 (Year of publication/validation).

Web Site: creativecommons.org/licenses/by/4.0/deed.en

Commercial Use: No

Reference’s

Herranz-Pascual, K., Iraurgi, I., Aspuru, I., Garcia-Pérez, I., Eguiguren, J. L., & Santander, Á. (2023). Development of the Acoustic Comfort Assessment Scale (ACAS-12): Psychometric properties, validity evidence and back-translation between Spanish and English. PLoS ONE, 18(2), Article e0281534. doi.org/10.1371/journal.pone.0281534

Items of the Acoustic Comfort Assessment Scale (ACAS-12)

The Acoustic Comfort Assessment Scale (ACAS-12) contains 12-pair items, rated on a 5-point semantic differential scale. Specific item details are available in the supplemental material of the source reference.