Mobile phones: A trade-off between speech intelligibility and exposure to noise levels and to radio-frequency electromagnetic fields

2019 · Mixed · Moderate evidence

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MixedModerate evidencePaper 1804

Study snapshot

Publicationmanual · 2019

Study typeexposure_assessment

Reported directionMixed

Evidence ratingModerate

Abstract

Mobile phones: A trade-off between speech intelligibility and exposure to noise levels and to radio-frequency electromagnetic fields Thielens A, Bockstael A, Declerck S, Aminzadeh R, Aerts S, Botteldooren D, Martens L, Wout J.Mobile phones: A trade-off between speech intelligibility and exposure to noise levels and to radio-frequency electromagnetic field. Environmental Research. Published online May 8, 2019. doi.org. Highlights • First time measurement of simultaneous head exposure to RF-EMF and sound pressure during smartphone usage. • Three use cases are compared: smartphone use at the ear, in speaker mode, and with a headset. • We demonstrate that exposure to RF-EMF and sound pressure is highest when a phone held at the ear during calls. • Speech intelligibility is more favourable when the phone is held at the ear in different background noise conditions. • We demonstrate that reductions in exposure might come at a cost of speech intelligibility during wireless phone calls. Abstract When making phone calls, cellphone and smartphone users are exposed to radio-frequency (RF) electromagnetic fields (EMFs) and sound pressure simultaneously. Speech intelligibility during mobile phone calls is related to the sound pressure level of speech relative to potential background sounds and also to the RF- EMF exposure, since the signal quality is correlated with the RF-EMF strength. Additionally, speech intelligibility, sound pressure level, and exposure to RF-EMFs are dependent on how the call is made (on speaker, held at the ear, or with headsets). The relationship between speech intelligibility, sound exposure, and exposure to RF-EMFs is determined in this study. To this aim, the transmitted RF-EMF power was recorded during phone calls made by 53 subjects in three different, controlled exposure scenarios: calling with the phone at the ear, calling in speaker-mode, and calling with a headset. This emitted power is directly proportional to the exposure to RF EMFs and is translated into specific absorption rate using numerical simulations. Simultaneously, sound pressure levels have been recorded and speech intelligibility has been assessed during each phone call. The results show that exposure to RF-EMFs, quantified as the specific absorption in the head, will be reduced when speaker-mode or a headset is used, in comparison to calling next to the ear. Additionally, personal exposure to sound pressure is also found to be highest in the condition where the phone is held next to the ear. On the other hand, speech perception is found to be the best when calling with a phone next to the ear in comparison to the other studied conditions, when background noise is present. Excerpt To our knowledge, this is the first study that reports SAR values and emitted powers obtained using actual phone calls made by several volunteers in controlled exposure conditions. In addition, it is also to the authors' best knowledge, the first paper studying the joint exposure to sound and RF-EMF.... Conclusions In this study, the transmitted radio-frequency electromagnetic field (RF-EMF) power was recorded for 53 subjects who carried out phone calls in three controlled exposure scenarios: calling with the phone at the ear, calling in speaker-mode, and calling with a headset. Phone calls were carried out using the Wideband Code Division Multiple Access (WCDMA) and Global System for Mobile communication (GSM) technologies. For both communication technologies, the emitted power of the phone at the ear was higher than the emitted power in the two other exposure conditions. Moreover, Finite-Difference Time-Domain simulations for a fixed emitted power showed that the brain-averaged specific absorption rate (SARbrain) was higher when the emitting antenna was located close to the ear than in speaker-mode and headset (94-350 times higher). The SARbrain values were then rescaled using the measured powers emitted using GSM technology during the experiments in order to estimate the RF-EMF absorption in the three studied scenarios. It was concluded that the SARbrain will be reduced by more than a factor 100 when either speaker-mode or a headset are used, in comparison to calling next to the ear. These results can be used as additional input for governmental institutions that issue guidelines on smart phone usage with the aim of lowering exposure. Furthermore, in conditions where background noise was present, speech perception was found to be the best when the phone was held at the ear in comparison to using the phone in speaker mode or with a headset. However, the exposure to sound pressure was also found to be the highest in the at-ear configuration, while it was lowest with the phone in speaker mode. Overall, the speaker-mode condition was found to be the configuration in which both exposures to RF-EMFs (in terms of SARbrain) and sound pressure were lowest, although reducing exposure by changing to this configuration does come at a cost in terms of speech intelligibility, in particular in noisy environments. Using a wired headset, on the other hand, was found to significantly reduce SARbrain while only reducing speech intelligibility by a small, yet significant in noisy conditions, amount in comparison to using the phone at the ear. These results are important for smartphone users that might be concerned about both exposure during their calls and about the quality of their calls. sciencedirect.com

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeexposure_assessment

Effect directionmixed

Population53 subjects making phone calls in controlled scenarios

Sample size53

ExposureRF

Evidence strengthModerateConfidence: 78% · Peer reviewed: yes

Main findings

In 53 subjects, transmitted RF-EMF power and estimated SARbrain were higher when calling with the phone at the ear than when using speaker mode or a headset. Sound pressure exposure was also highest in the at-ear condition, while speech perception in background noise was best with the phone at the ear; speaker mode yielded the lowest RF-EMF (SARbrain) and sound pressure but reduced speech intelligibility, particularly in noisy environments.

Outcomes measured

Transmitted RF-EMF power during phone calls
Estimated head/brain-averaged SAR (SARbrain) via numerical simulations
Sound pressure level exposure during calls
Speech intelligibility/speech perception during calls (including with background noise)

Limitations

Specific RF frequencies are not reported in the provided abstract/metadata (technologies mentioned: GSM and WCDMA).
SAR values are estimated using numerical simulations and rescaled using measured emitted powers rather than directly measured in vivo.
Controlled exposure scenarios may not reflect all real-world calling conditions.

View raw extracted JSON

{
  "study_type": "exposure_assessment",
  "exposure": {
    "band": "RF",
    "source": "mobile phone",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "53 subjects making phone calls in controlled scenarios",
  "sample_size": 53,
  "outcomes": [
    "Transmitted RF-EMF power during phone calls",
    "Estimated head/brain-averaged SAR (SARbrain) via numerical simulations",
    "Sound pressure level exposure during calls",
    "Speech intelligibility/speech perception during calls (including with background noise)"
  ],
  "main_findings": "In 53 subjects, transmitted RF-EMF power and estimated SARbrain were higher when calling with the phone at the ear than when using speaker mode or a headset. Sound pressure exposure was also highest in the at-ear condition, while speech perception in background noise was best with the phone at the ear; speaker mode yielded the lowest RF-EMF (SARbrain) and sound pressure but reduced speech intelligibility, particularly in noisy environments.",
  "effect_direction": "mixed",
  "limitations": [
    "Specific RF frequencies are not reported in the provided abstract/metadata (technologies mentioned: GSM and WCDMA).",
    "SAR values are estimated using numerical simulations and rescaled using measured emitted powers rather than directly measured in vivo.",
    "Controlled exposure scenarios may not reflect all real-world calling conditions."
  ],
  "evidence_strength": "moderate",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "mobile phone",
    "smartphone",
    "RF-EMF",
    "GSM",
    "WCDMA",
    "specific absorption rate",
    "SARbrain",
    "sound pressure level",
    "speech intelligibility",
    "speaker mode",
    "headset",
    "exposure assessment",
    "numerical simulations",
    "FDTD"
  ],
  "suggested_hubs": [
    {
      "slug": "mobile-phones",
      "weight": 0.95,
      "reason": "Study measures emitted power and estimates SAR during smartphone calls across use configurations."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1016/j.envres.2019.05.006
PubMed: Not supplied

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