What makes an opera singer stand out? New research decodes 'black box' of opera evaluation

Researchers statistically investigate key factors that contribute to an opera singer’s overall score in singing competitions

Keio University Global Research Institute

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

A new study led by researchers from Keio University in Japan offer important insights into the key factors determining the scores of aspiring opera singers in singing competitions, providing a scientific approach to their training and education. The study revealed that perceived vibrato and singing power ratio or the singer’s formant are the key predictors of good scores in opera singing competitions.

view more 

Credit: Haruka Kondo from Keio University

Opera singers are admired for their powerful and expressive voices, achieved through years of rigorous training. In opera singing competitions, judges evaluate the performances of aspiring singers by assigning an overall score to the singer’s voice that decides their ranking. These scores, however, determine not just the outcome of a single event but the overall trajectory of a singer’s career. Yet, the criteria underlying these scores have remained a mystery. More specifically, it is unclear exactly what specific aspects of a singer’s voice influence their score.

Previous studies have suggested that certain qualities—such as vibrato, resonance, timbre, and diction (the style of enunciation)—play a role. In addition, acoustic features play an important role in such evaluations, especially when based on audio recordings. One key acoustic feature in this regard is the singer’s formant, or the ability of their voice to fill a large hall without amplification. This can be quantified using the singing power ratio (SPR), which measures the energy balance of a voice in a specific range of frequencies. Other indicators include the harmonic-to-noise ratio (HNR), which represents the clarity of a voice, and the integrated loudness units full scale (LUFS), a standardized metric used for normalizing audio. But, which of these factors matter most when judges assign scores?

A new study has now found a clear answer to this question. Led by Ms. Haruka Kondo, a PhD student at the Graduate School of Media and Governance at Keio University, Japan, researchers conducted a statistical analysis of opera performance recordings to identify key factors contributing to the singers’ scores in singing competitions. “For singers, a competition score can define their career, but what it is the judges are listening for has remained subjective and unclear,” explains Ms. Kondo, herself a soprano opera singer. “In our study, we scientifically decoded how different vocal and acoustic factors influence judgment scores in opera singing competitions.”

The research team was headed by Associate Professor Shinya Fujii and included Dr. Sotaro Kondoh, a JSPS Research Fellow, from the Faculty of Environment and Information Studies at Keio University. The study was published in Volume 16 of the journal Frontiers in Psychology on August 08, 2025.

Ten trained Japanese female opera singers participated in the study, with each performing the classical Italian song “Caro mio ben” under standard recording conditions. These recordings were then rated by four vocal instructors, who were also professional singers. They assigned both an overall score out of 100 as well as scores on six vocal attributes: vibrato, resonance, timbre, diction, intonation, and expressiveness. Each singer was evaluated by all the judges in random order. Additionally, the researchers analyzed the acoustic features of the recordings using three parameters, namely SPR, HNR, and LUFS.

To understand the contribution made by the vocal attributes and the acoustic features on the overall score, the team then developed two models. One of them examined the impact of the six vocal attributes, while the other investigated the contribution from the acoustic features.

Remarkably, the results suggested two main predictors of scores: vibrato and SPR. Vibrato, known to have a strong correlation with overall scores from previous studies, stood out as the most significant vocal attribute, with the impact of the other attributes being statistically insignificant. The significance of SPR among the acoustic features was consistent with its known role as an indicator of the singer’s formant. In contrast, HNR and LUFS did not significantly impact the score. The low impact of HNR was explained by the fact that trained singers already exhibit high clarity and low irregularity in their voice. Similarly, loudness alone being a weak contributor toward subjective evaluations explained the low impact of LUFS.

“These findings provide a clearer picture of how judges evaluate performances,” notes Dr. Fujii. “Our research offers objective insights and powerful new tools for vocal training and education. Beyond that, it also addresses foundational questions of how humans perceive sound and art.”

“Imagine a voice lesson where instead of relying solely on the teacher’s perception, students can reliably track specific characteristics of their voice on a screen,” remarks Dr. Kondoh.

Overall, the study could provide a firm scientific foundation for understanding what makes an opera singer sound better and possibly bridge the gap between the art of opera singing and the science of acoustics.

 

***

Reference

DOI: https://doi.org/10.3389/fpsyg.2025.1568982

 

About Keio University Global Research Institute (KGRI), Japan

The Keio University Global Research Institute (KGRI) was established in November 2016 as a research organization to bridge faculties and graduate schools across the university. KGRI aims to promote interdisciplinary and international collaborative research that goes beyond the boundaries of singular academic disciplines and international borders. It also aims to share research outcomes both in Japan and worldwide, further promoting engagement in joint research. To enhance those activities above, in 2022, Keio University set its goal of becoming a “Research university that forges the common sense of the future”.

Website: https://www.kgri.keio.ac.jp/en/index.html

About Haruka Kondo from Keio University

Haruka Kondo is a PhD student specializing in vocal science at the Graduate School of Media and Governance, Keio University. Alongside her academic pursuits, she is an accomplished operatic soprano and a representative of Opera Lab Japan. She was awarded third prize at the 2025 New York International Classical Music Competition.

https://researchmap.jp/haruka__kondo

About Associate Professor Shinya Fujii from Keio University

Shinya Fujii obtained his MS and PhD degrees in Human and Environmental Studies from Kyoto University in 2007 and 2010, respectively. He currently serves as an Associate Professor at the Faculty of Environment and Information Studies at Keio University and is also the Director of the Neurosciences and Music Laboratory at Keio University and the Research Center for Music Science at Keio University Global Research Institute. Dr. Fujii specializes in perception neuroscience and its relationship with music and has over 75 papers credited to his name.

https://neuromusic.sfc.keio.ac.jp/

https://www.kgri.keio.ac.jp/en/project/research-centers/2024/A24-28.html

https://www.k-ris.keio.ac.jp/html/100012635_en.html

https://researchmap.jp/7000025148?lang=en

About Sotaro Kondoh from Keio University

Dr. Sotaro Kondoh is a Japan Society for the Promotion of Science Research Fellow and Visiting Research Fellow at Keio University. His research focuses on musical meter, beat, and rhythm perception. He also investigates music chills, musical interaction, social bonding, and respect-related emotions, employing methodologies such as electroencephalogram, heart rate assessment, and psychophysical measurements.

https://researchmap.jp/sotaro_kondoh?lang=en

Funding information

This work was supported by the Taikichiro Mori Memorial Research Grant, the JST SPRING program (Grant No. JPMJSP2123), and the JSPS KAKENHI (Grant No. 24H02199).

---

Journal

Frontiers in Psychology

DOI

10.3389/fpsyg.2025.1568982 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Perceived vibrato and the singing power ratio explain overall evaluations in opera singing

Article Publication Date

8-Aug-2025

 

Unveiling the mechanism behind sea urchin twinning

University of Tsukuba

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Early sea urchin embryos can be split into two, and each half can develop into a complete individual. In other words, they can produce identical (monozygotic) twins—a phenomenon known as regulative development. However, the mechanism by which identical twinning occurs has long remained unclear.

view more 

Credit: Shunsuke Yaguchi

Tsukuba, Japan—In the late 19th century, German embryologist Hans Driesch showed that when fertilized sea urchin eggs were separated at the two-cell stage, each cell could still develop into a complete organism. Yet, for more than a century, the developmental process and molecular mechanisms that allow the embryo to re-establish its body axes (anterior-posterior, dorsal-ventral, and left-right) and resume normal development have remained largely unclear.

In this study, researchers combined advanced microscopy with molecular biology to uncover how each embryo fragment is able to reset its developmental blueprint and grow into a full individual. They also succeeded in visualizing axis reconstruction by tracking the cellular movements and activation of gene that drives this remarkable self-organizing ability.

This discovery offers fresh insight into a long-standing question in life sciences: how two complete individuals can emerge from one fertilized egg. Using sea urchins as a model, it may also provide valuable insights for future developmental studies, including the origins of monozygotic twinning in humans.

###
This work is supported by JST PRESTO Grant number JPMJPR194C, JST A-STEP Grant number JPMJTR204E, JSPS KAKENHI Grant number 23K23933 and 24K21959 to S.Y., and JST PRESTO Grant number JPMJPR1945 and JSPS KAKENHI Grant Numbers 19K20406 and 23K11312 to K.T.

 

Original Paper

Title of original paper:
Unraveling the regulative development and molecular mechanisms of identical sea urchin twins

Journal:
Nature Communications

DOI:
10.1038/s41467-025-63111-z

Correspondence

Associate Professor YAGUCHI, Shunsuke
Institute of Life and Environmental Sciences, University of Tsukuba

Specially Appointed Lecturer TSUYUZAKI, Koki
Department of Artificial Intelligence Medicine, Graduate School of Medicine, Chiba University

Related Link

Institute of Life and Environmental Sciences

---

Journal

Nature Communications

DOI

10.1038/s41467-025-63111-z 

Article Title

Unraveling the regulative development and molecular mechanisms of identical sea urchin twins

Article Publication Date

5-Sep-2025

 

Bark beetles reshape forest microclimate – but deciduous trees can help

Stockholm University

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Caroline Greiser installing a microclimate sensor in a bark beetle attacked forest stand. Photo: Mark Ghaly

view more 

Credit: Mark Ghaly

A new study from Stockholm University reveals that spruce bark beetles, already infamous for killing millions of trees in Sweden, are also changing the forest microclimate. Using a combination of temperature sensors attached to trees and thermal drone imagery, researchers found that beetle-attacked forests can heat up by as much as two degrees during summer days – but deciduous trees helped to cool down attacked forest stands.

The research, conducted in Södermanland, Sweden, measured how bark beetle damage affects the microclimate both below the canopy and at canopy level. The findings suggest that forest disturbances not only respond to climate change, but also feed back into it by creating novel temperature regimes.

“We’ve known for a long time that hot, dry summers increase bark beetle outbreaks,” says Caroline Greiser, lead author of the study and researcher at the Department of Physical Geography and the Bolin Centre for Climate Research. “But here we show the reverse: bark beetles themselves create new thermal environments in forests.”

Forest microclimates are often a bit cooler during the day and warmer during the night compared to open surroundings, leading to a buffering of warm and cold temperature extremes. The team set up a network of temperature sensors at 31 forest sites in five nature reserves in Södermanland, south of Stockholm, to study the microclimate in attacked and healthy forest stands. In one of the areas, Ekeby nature reserve, they also created temperature maps of the canopy surface with the help of a drone.

They found that dead trees were on average over 2°C warmer than living trees on sunny days, and that these “skeleton forests” with attacked and killed trees allowed more warming solar radiation to reach the understory. This could have knock-on effects on forest biodiversity, tree seedling survival, and even human comfort during heat waves.

However, there was one silver lining.

 “Where there were more deciduous trees like birch or aspen, the warming effect during the day was much smaller,” says Greiser. “And, opposed to our expectations, we didn’t see colder nights in beetle-attacked forests. The canopy cover was still high enough to slow down heat radiation during the night – so these stands may still protect young trees and other species from frost.”

The results have clear implications for forest management in a warming climate.

“Our study adds a new reason to diversify forests,” Greiser says. “Mixed stands with more deciduous trees are not only less vulnerable to beetle outbreaks, but they also help to keep the forest cooler afterwards.”

But what to do with the already damaged forests? From a microclimate perspective, the dead trees seem to provide a similar protection against night frost as shelterwood and therefore could be left standing instead of being salvage logged.

The researchers hope that their findings can guide decisions about post-disturbance regeneration, conservation area management, and salvage logging – all of which are critical in an era of more frequent extreme weather and pest outbreaks.

More information
The article “Bark beetles as microclimate engineers – thermal characteristics of infested spruce trees at the canopy surface and below the canopy” is published in Agricultural and Forest Meteorology. Authors: Greiser, C., Huo, L., Ghaly, M., Brown, I., Metsu, C., Van Meerbeek, K., & Lehmann, P. (2025).
https://www.sciencedirect.com/science/article/pii/S0168192325004150

Contact:
Caroline Greiser
Department of Physical Geography, Stockholm University
Bolin Centre for Climate Research
E-mail: caroline.greiser@su.se

Funding
This work was funded by the Oscar and Lilli Lamm Foundation [project grant to PL], the Bolin Centre for Climate Research [project grant to CG, PL, IB], the Swedish Research Council Formas [project grant 2021-01993 to CG; project grant 2024-00404 to LH], Internal Funds of KU Leuven [project grant C14/22/067 to KVM and CM].

Microclimate sensor at one of the 31 forest sites. The researchers used data from one of the two sensors, which was attached to the north side of a tree under a white radiation and rain shield, measuring air temperature at 2.0 m height. Photo: Caroline Greiser

Synthetic hemispheric canopy image taken with a smartphone and used to calculate how much more open the canopy is due to bark beetle attacks. Photo: Caroline Greiser

Journal

Agricultural and Forest Meteorology

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

“Bark beetles as microclimate engineers – thermal characteristics of infested spruce trees at the canopy surface and below the canopy”

 

New study shows proactive forest management reduces high severity wildfire by 88% and stabilizes carbon during extreme droughts

Vibrant Planet

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

Truckee, CA (5 September 2025) -- New research finds that treated forests are 88% less susceptible to high severity wildfire than their unmanaged counterparts, and can recover carbon stocks in only 7 years. The findings, carried out by researchers at Vibrant Planet, Northern Arizona University, American Forest Foundation, and Blue Forest, make the case for more proactive forest management across the US, and specifically, the increasingly wildfire-prone West. Read the publication in Frontiers in Forests and Global Change. 

Many forests in the West are adapted to live and thrive with frequent, low-severity fire. Yet the confluence of historical fire suppression, intensifying wildfire, and drought, are now rewriting the rules—and the risk—for forests and the communities that live in and around them. This work shows: without human stewardship designed to restore healthy fire regimes and forest structure, many of these fire-adapted forests will go up in flames and may never regenerate, instead transitioning to non-forested ecosystems.

“After 130 years of fire suppression, most of the western US is contending with an enormous wildfire debt ” said Katharyn Duffy, a study co-author and Senior Scientist at Vibrant Planet. “It’s not a question of if these forests will burn, but when, and where. Every year, we’re rolling the wildfire dice. One year, fires land in Arizona and New Mexico; the next, Oregon and Washington. But make no mistake—somewhere in the West, the dice always fall.”

As climate-driven megafires and prolonged droughts reshape California’s forests, this new peer-reviewed study offers hope—and hard evidence—that proactive forest treatments can tip the scales back toward resilience. The study analyzed over 200 fuel reduction projects across the Central Sierra in California and found that treated forests stored carbon more durably, matching or exceeding untreated areas by year seven—even after the extreme 2020–21 drought and megafires.

The study, which analyzed 216 thinning treatments implemented in California’s Central Sierra in 2016 and monitored wildfires that occurred through 2023, found that proactive forest management reduced average wildfire severity by 32% and cut the occurrence of high-severity fire by 88%. Treated areas not only burned less severely but also showed greater stability of live carbon, maintaining or exceeding baseline carbon levels by year seven despite the extreme drought and megafires of 2020–21. Treatments that were larger than six hectares or that received follow-up maintenance, such as prescribed burning or additional fuel removal, delivered the strongest fire-risk reduction and carbon-stabilization benefits. 

The researchers focused on California's fire-prone Sierra Nevada region (including portions of the recent Dixie, Caldor, and North Complex megafires) to assess how forest treatments affect wildfire resilience. They compared similar forests—some thinned in 2016, others untouched—creating a natural experiment to track outcomes over five years of drought and wildfires. 

The need for a natural experiment approach became apparent as researchers experienced the challenges of capturing recent wildfire impacts. “We started by trying to simulate current wildfire behavior, but we found that models failed to predict the extent and severity of fire conditions in 2020 and 2021,” said Ethan Yackulic, the lead author of the study. “For example, the nine largest fires in California’s history have all occurred in the past decade. This kind of natural experiment gives us verifiable insights into how forests are truly faring because no model is going to predict what we’re witnessing right now.”

Yackulic explains, “even though the treatments we monitored had a high initial 'carbon cost' in the removal of live trees, a dramatic signal of forest resilience emerged in subsequent years. While other studies have shown that management interventions are effective at reducing wildfire hazard risk on a treatment-by-treatment basis, it was encouraging to witness landscape scale treatment effectiveness and the potential for more durable carbon storage across the Central Sierra Nevada.” 

Sophie Gilbert, a study co-author and Director of Science Strategy at Vibrant Planet, said these results help answer one of the central questions facing land managers today: “How much treatment would we have to do, how intensely, and where, to reduce a forest’s risk to severe fire, and drought?” Gilbert said part of that answer is not just calibrating intensity of fuel treatments but committing to a sustainable relationship with the land. 

These results could support an additional source of funding for forest restoration and management efforts, recent research from Blue Forest suggests, while keeping forests and their many ecosystem benefits intact. “Treating forests is about re-establishing humans’ reciprocal relationship with the land. It requires sustained attention and effort. And in return, forests will reward us with abundant ecosystem services. One of these is keeping carbon out of the atmosphere, but so many others come along for the ride: water quality and quantity, biodiversity, and more.” said Gilbert.

### 

About Vibrant Planet

Vibrant Planet helps land managers, fire districts, county supervisors, and more, prioritize where they can buy down the most wildfire risk, protecting our communities and ecosystems. Our advanced technology and fire science streamlines the development of wildfire risk mitigation plans that can adapt to change on the ground. www.vibrantplanet.net

 

Funding Sources

Funding information: Award number: 24-CA-11132544-064. This work was partially funded by the American Forest Foundation, as a recipient of an award from the USDA Forest Service #24-CA-11132544-064 Removing Barriers to Scaling the Family Forest Carbon Program and Market Opportunities for Family Forest Landowners.

---

Journal

Frontiers

DOI

10.3389/ffgc.2025.1498430 

Article Title

Rising from the ashes: treatments stabilize carbon storage in California’s frequent-fire forests

Article Publication Date

5-Sep-2025