## 1 Introduction  
The still ongoing pandemic of the COVID-19 virus has had a huge impact on many aspects of human activities and interaction [1, 2]. The academic world was no exception, as it had to resort to distance learning, but also to remote research in many fields, mostly through various online platforms [3, 4, 5, 6, 7, 8, 9, 10]. Even before the pandemic, the field of acoustics that investigates perceptual phenomena by performing listening tests has already been contemplating the idea to perform online listening tests for some time [11], and the same idea can be applied to other fields such as speech audiometry [12, 13]. The pandemic itself has sped up the use of such an approach. The beginnings of this approach were focused on the possibility of distributing and performing online tests anywhere through available means of electronic communication, thus making them accessible to a pool of potential test subjects that is considerably larger than the one available in a laboratory. Experiments performed remotely suffer from the lack of control over the experimental conditions, leading to question to what degree the collected experimental data is reliable [14, 15, 16]. When it comes to online listening tests, it is entirely up to the test subject to follow the guidelines provided by the experiment designer regarding the acoustics of the room and the background noise inside, and the type and characteristics of the sound reproduction system (loudspeakers or headphones) to be used. Some types of investigations of perceptual phenomena require a calibrated sound reproduction system in terms of exact level and/or flat frequency response, making them suitable only for a controlled laboratory environment. Other types of tests are not as sensitive to the lack of exact calibration and can be performed at home. In any case, any kind of calibration performed on a home listening test setup proves to be a herculean task, as the test subjects have no access to the equipment necessary for performing the calibration. This issue is often mentioned in reports on remotely performed research, but no suggestion is given on how to tackle it. To solve at least a part of this problem that deals with the calibration of the reproduction level, the authors claim that it is possible to perform such a calibration using sounds people are familiar with from everyday experience, namely, speech. The accuracy of such a procedure needs to be evaluated, but the assumption is that it is sufficient for non-critical online listening test applications. The test subjects in online listening tests are likely to use both headphones and loudspeakers, i.e., whatever is available to them. The levels required for headphone and loudspeaker reproduction that elicit the same sense of loudness differ by about 6 dB in anechoic conditions, as documented in literature [17; 18; 19; 20] as \"the 6-dB mismatch\". Studies show that the mismatch depends on the spectral content of the presented sound, the acoustics of the room and even the type of headphones used [21; 22], and that it can be avoided by careful equalization at the eardrum of the listener [23; 24]. However, as the level calibration method proposed in this paper is intended for use in non-laboratory conditions, this mismatch is inevitable and needs to be accounted for in the calibration procedure. The first part of this study examines the consistency of the test subjects as listeners in setting what they consider to be the \"normal\" level of reproduced speech depending on the voice of the speaker, the sound reproduction system used (loudspeakers or headphones), and the (non)existence of a visual stimulus that represents the interlocutor. In studies [25; 26], it is suggested that people tend to associate loudness of speech with average levels, whereas the loudness of non-intelligible sounds is strongly associated with their peak levels. Moreover, it is also suggested that people are more consistent in setting the level of speech than they are when asked to set the level of non-speech sounds.