I Kill by Giorgio Faletti Page A

are the frequency. The yellow line is the analysed voice. If you take Verdier’s voice from different points of the recording and overlap them, they match
perfectly.’ He looked round to see if his audience were keeping up.
    ‘This is the other voice.’ Clavert returned to the previous screen, clicking the purple line. The graph appeared again, but this time the yellow line was broken and the field was
much smaller. ‘In this case, the caller passed his voice through filters to distort and compress the sound, mixing vocal frequencies and making it unrecognizable. All you have to do is change
just one of the filters slightly to get a different graph each time.’
    ‘Can we analyse the recording to find out the model of the equipment he used?’ Hulot asked. ‘Maybe we could find out who sold it.’
    ‘I don’t think so,’ the technician said doubtfully. ‘You can buy these machines just about anywhere. There are several brands. Performance varies according to the
specification and the brand but they all do basically the same thing. And electronics change all the time so there’s a big second-hand market. All this stuff generally ends up in the hands of
home-recording enthusiasts, and almost always without receipts. I really don’t think it’s feasible.’
    ‘We’ll see what we can do,’ Froben joined in, without seconding Clavert’s pessimism. ‘We’ve got so little solid information that we can’t overlook
anything.’
    Hulot noticed Frank looking around, apparently absorbed in his own thoughts, as if he already knew all this. Still, the inspector was sure that he had heard every word and was filing it all
away. He turned back to Clavert.
    ‘And what can you tell us about the fact that the phone call didn’t go through the switchboard?’
    ‘Well, I can’t actually advance a theory about that. I can think of two basic possibilities. All switchboards have numbers that let you through. If you know them, you can avoid the
switchboard operators. Radio Monte Carlo certainly isn’t NASA as far as secrecy is concerned, so it wouldn’t be hard for someone to get his hands on the numbers. The second hypothesis
is a little more complicated, but it’s not science fiction. Actually, I think it sounds more likely.’
    ‘And that is?’
    ‘I made some enquiries,’ Clavert said, leaning back in his chair. ‘The Radio Monte Carlo switchboard, like most stations that run phone-ins, has a computer program with a
function that displays the caller’s number, for obvious reasons.’ Again he looked around at the three detectives. ‘When the call came, no number appeared on the display, which
means that the person calling had attached an electronic device to the phone that neutralized the switchboard function.’
    Hulot shook his head. ‘Is that hard to do?’
    ‘Anyone who knows electronics and telephones wouldn’t have any problem. Any reasonably competent hacker could do it through the Internet.’
    ‘Can we find out whether the call came from a land line or a mobile phone?’ Hulot felt like a prisoner with walls everywhere he looked.
    ‘No, but I’d exclude a mobile. If he used the Web, mobiles are much slower and don’t work as accurately. The person who did all that is too knowledgeable not to be aware of
it.’
    ‘Any more tests you can do on the recording?’
    ‘Not with the equipment I have. I’m going to send a copy of the DAT to the science lab in Lyons to see if they can get anything out of it.’
    ‘Good. Top priority,’ Hulot said, resting his hand on Clavert’s shoulder. ‘If Lyons complains, we’ll pressure them.’
    Clavert considered the subject closed. He unwrapped a stick of gum and put it in his mouth. There was a moment of silence. The four of them, each in his own way, thought through what had been
said. Froben spoke first.
    ‘Come on, let me get you some coffee.’
    He led them up the stairs and turned left at the landing. There was a coffee machine in the